Users' evaluations of four electronic travel aids aimed at navigation for persons who are visually impaired.
Visually disabled persons
Visually disabled persons (Research)
Electronic traffic controls (Usage)
Roentgen, Uta R.
Gelderblom, Gert Jan
de Witte, Luc P.
|Publication:||Name: Journal of Visual Impairment & Blindness Publisher: American Foundation for the Blind Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2011 American Foundation for the Blind ISSN: 0145-482X|
|Issue:||Date: Oct-Nov, 2011 Source Volume: 105 Source Issue: 10|
|Topic:||Event Code: 310 Science & research|
|Product:||Product Code: 3662373 Controllers, Signal NAICS Code: 33429 Other Communications Equipment Manufacturing|
|Geographic:||Geographic Scope: Netherlands Geographic Code: 4EUNE Netherlands|
Abstract: Eighteen persons with visual impairments evaluated four
systematically selected navigation systems. Their performance on 11
tasks, provided ratings, satisfaction on seven aspects of the assistive
devices, and explanatory comments show generally valuable functionality
and usability, as well as individual marked preferences for various
features of different navigation systems.
Various studies have reported that restrictions in outdoor mobility and independent travel are among the prominent areas of concern in the everyday lives of persons who are visually impaired (that is, those who are blind or have low vision) (Brouwer, Sadlo, Winding, & Hanneman, 2008; Douglas, Corcoran, & Pavey, 2006; Marston & Golledge, 2003). Their process of mobility was depicted by Leonard (1972), who identified two major components: the detection of objects and orientation. Leonard divided orientation into near orientation ("the traveller's ability to maintain his moment-to-moment relationship to the immediate environment") and far orientation ("the traveler's ability to follow a route") (p. 40). Bentzen
This study was funded by a grant from the InSight program of ZonMw. The authors thank all the participants and experts for their valuable contributions and the O&M specialists and employees of Royal Visio for their cooperation. They gratefully acknowledge HumanWare, Optelec, and Wayfinder for lending them the devices. (1997) listed three categories of orientation aids: models, maps, and verbal aids. She hypothesized: "Electronic technology makes it possible to randomly access verbal orientation information such as geographic information systems (GISs), which are electronic databases of spatial information. Coupled with position tracking technology, GISs could revolutionize the way some persons navigate the environment" (p. 284).
Since the introduction of the Global Positioning System (GPS), research projects have investigated its application in combination with geographic information systems for persons who are visually impaired. The Personal Guidance System (Golledge, Marston, Loomis, & Klatzky, 2004), MoBIC (Petrie et al., 1997), and Drishti (Helal, Moore, & Ramachandran, 2001) are apt examples. In 2000, GPSTalk, the first electronic travel aid aimed at navigation, became commercially available (May & LaPierre, 2007). GPS-based systems are widely used for civilian applications, but evidence of their effectiveness for persons who are visually impaired is sparse. In a systematic review, Roentgen, Gelderblom, Soede, & de Witte (2009) found only two such studies. In both studies (Ponchillia et al., 2007; Ponchillia, Rak, Freeland, & LaGrow, 2007), BrailleNote GPS was proved to be effective in locating a target, having time to reorient, and reaching a target location. In addition, Havik, Steyvers, van der Velde, Pinkster, and Kooijman (2010) found improvement in Trekker users' self-reported orientation and mobility (O&M) skills and a change in attitude toward feeling safer and more independent. The purpose of the study presented here was to investigate the functionality and usability of different navigation systems for persons who are visually impaired.
In fall 2009, we conducted a user evaluation of 4 electronic travel aids. A previous search had revealed 23 devices that persons who are visually impaired can use without environmental adaptations (Roentgen, Gelderblom, Soede, & de Witte, 2008). The devices were classified into two main categories: (1) those aimed at detecting obstacles and orientation (n = 13) and (2) navigation systems (n = 10).
We selected the four navigation devices for the 2009 study on the basis of their availability in the Netherlands, evidence of promising potential (Roentgen et al., 2009), advice from experts, and functionality (Roentgen & Gelderblom, 2008). As a result, we chose the Braille-Note GPS, Trekker, Trekker Breeze, and Wayfinder Access. Important features of these devices are presented in Table 1.
The sample consisted of healthy, community-dwelling adults with severe visual impairments, who were recruited through Viziris, the Dutch association of clients who are visually impaired. Persons who were willing to take part received detailed information. They underwent no ophthalmologic examination before their inclusion; their diagnoses, severity of visual impairments, and functional consequences of their visual impairments were self-reported. The following criteria were established for inclusion: The participants had to be able to travel outside their homes independently but be reliant on a mobility aid (a dog guide or a long cane), have basic computer skills, and be aged 18 or older. Exclusion criteria were any cognitive or additional motor or physical mobility impairment. Twenty-one persons enrolled, of whom 18 participated.
A 20-item questionnaire on demographic and background information, including the etiology, type, and severity of the visual impairment and the resulting functional consequences for daily living, especially on outdoor mobility, was sent to the participants via e-mail prior to the tests. Appointments were made individually for participants to spend one day taking tests at one of the major service providers for persons who are visually impaired in the Netherlands. On the test day, each participant signed the informed consent form. In the morning, instruction and training with the first navigation system was provided, confined to the operation of the device in performing 11 tasks. When the participants felt ready, they were asked to perform these tasks as test situations. This practical part was followed by a semistructured interview. After a lunch break, the procedure was repeated for the second navigation system, followed by questions on both devices. All the interviews were recorded and transcribed verbatim.
Each participant tested two of the four selected devices, so that every device was evaluated by nine participants, and all possible combinations of devices were tested three times. If the participants had experience with one of the tested navigation systems, they evaluated two others.
As is depicted in Table 2, 11 tasks were selected. These tasks were first used to guide instruction and training and then in test situations, and they were intended to enable the participants to gain insights into the basic functionality of the devices. An essential part was traveling an unknown outdoor route in a residential area (see Figure 1), including different sections of a footpath and pavement and five turns at no traffic light-controlled intersections, of which one was a roundabout. Crosswalks were indicated by curb ramps and markings on the road surface. Apart from turns at intersections, the participants had to cross between two and four side streets, depending on which side of the street they walked. While completing the routes, the participants were followed by the experimenter (the lead author), who assured their safety. The time it took to perform the tasks, remarks on the performance of the participant and the device, and salient events were noted on an observation form. Although the participants were asked to complete the tasks as independently as possible, support with the operation of the devices was provided on request (comparable to consulting the user guide), and assistance was provided at difficult sections of the route (such as a roundabout) and to ensure safe street crossing.
The semistructured interviews were based on the D-Quest (Wessels & de Witte, 2003), combined with open questions concerning the participants' subjective experiences, and opinions about the use and functionality of the electronic travel aids. The participants rated their satisfaction with respect to seven aspects of the D-Quest--dimension, weight, adjustment, safety, simplicity, comfort, and effectiveness--on a 5-point scale (from 1 = not satisfied at all to 5 = very satisfied).
[FIGURE 1 OMITTED]
They were also asked to provide ratings (1-10) for the tested functionalities and their overall evaluation, as well as additional comments on the perceived added value of and difficulties with the devices. SPSS 16.0 statistical analysis software was used to analyze the quantitative data by applying descriptive techniques. With regard to the qualitative data, a content analysis of the transcriptions was performed.
DEMOGRAPHIC AND BACKGROUND INFORMATION
Eight participants (44.4%) described themselves as having very low vision, and the remaining 10 (55.6%) described themselves as being ("legally") blind. Of the 18 participants, 12 were male and 6 were female, with a mean age of 55 [+ or -] 12 years (range: 20-68 years). The participants reported the following diseases and disorders: retinitis pigmentosa, macular degeneration, glaucoma, choroideremia, Wagner's disease, Usher syndrome II, Coats' disease, and retinal detachment; one participant wore two ocular prostheses. Four participants were employed, their volume of employment ranging from 50% to 100%, and 14 were engaged in volunteer work.
All the participants reported that they frequently walked independently in familiar environments; however, 8 did not or did not often travel independently in an unknown environment. Five participants were satisfied with their ability to travel independently, 8 were more or less satisfied, and 2 were not satisfied. Seven participants were satisfied with their frequency of independent outdoor mobility, 4 sought to move around more frequently, and 4 were not satisfied. Fifteen participants mentioned that they would like to travel more routes independently, 8 of whom also said that these routes should be in familiar environments. Twelve participants stated that they occasionally refrained from certain activities because of mobility problems. All except 1 had received structured O&M training, and all the participants made frequent (14 daily) use of a personal computer for work and leisure purposes. While completing the route, 13 used a long cane, 1 used a dog guide in combination with the long cane, and 3 used only a dog guide. Five participants had gained prior experience in using a navigation system.
The analyzed data on the mean amount of time needed to complete a task showed, with few exceptions, comparable means per task for the evaluated devices, with large standard deviations relative to the mean, indicating its poor fit for describing the data and a high intersubject variability. Other reasons why task-completion time was a problematic measure for usability in the study are further explicated in the Discussion section. All tested functionalities were judged at a higher-thansatisfactory level with the exception of Trekker Breeze's "enter route" (5.1 [+ or -] 1.7). Trekker's "explore route in advance" (8.4 [+ or -] 0.9) and Trekker Breeze's "Where am I?" function (8.4 [+ or -] 0.9) were rated best. Mean ratings for all the tested functionalities were 7.2 for Trekker Breeze, 7.6 for BrailleNote and Wayfinder Access, and 8 for Trekker. Individual scores ranged from 6.6 to 9.4 (Braille Note) to 7 to 8.6 (Trekker) to 6.4 to 7.6 (Trekker Breeze) and to 6.2 to 9.9 (Wayfinder Access). All items of the D-Quest were judged better than the average score (more or less satisfied) with the exception of the dimensions (2.8) and comfort (3) of BrailleNote. The dimensions (4.4) and weight (4.8) of Wayfinder Access were rated best. The total scores obtained on the group level were 3.3 for BrailleNote, 3.8 for Trekker and Trekker Breeze, and 4.2 for Wayfinder Access. The total scores on the level of individual participants ranged from 2.3 to 4.7 (BrailleNote) to 3 to 4.7 (Trekker) to 3.3 to 4.3 (Trekker Breeze) and to 3.4 to 5 (Wayfinder Access). In the following sections, additional comments made by the participants during the interviews and the experimenter's observations during the performance of the tasks are summarized.
PARTICIPANTS' COMMENTS AND EXPERIMENTER'S OBSERVATIONS
All the devices
All the participants found the operation of the navigation systems not difficult or easy to learn (for persons with good computer skills). Assistance was needed only when a participant failed to follow the steps in the correct order. With all the devices, there was no delay in establishing a GPS fix after starting up.
The "explore route in advance" function was found to be useful for getting an impression of the route and hearing the street names prior to traveling. The participants expressed different preferences concerning input and data entry and different thoughts about the menu structure of the devices. They judged the menu structure as intuitive or not intuitive or logical, and preferred to navigate through a menu or a list of street names or to enter full text. Accordingly, the participants had different opinions about the manner of input: QWERTY, SMS style, hot keys, shortcut keystrokes, first-letter navigation, and the property of keys and buttons that they stated were easily or not easily discernable. The participants' opinions also diverged on the quantity and detail of the information that was provided, especially with respect to the announcements made during route guiding and points of interest: Some participants appreciated detailed information and evaluated it as high quality and comprehensive, whereas others considered it too much information and favored additional information on request. Comparably, the participants' thoughts differed on confirmation of the current position after turns and at regular intervals; confirmation that they were on route; and announcements of streets and side streets, the next intersection, and the heading.
Regarding route following, some participants stated that they felt "very safe" while traveling this route in an unknown environment, assuming that they had reached their destination without the assistance of a human guide (with the exception of crossing the street at the roundabout by some), experienced low levels of stress while traveling, and had no fear of losing their way. Others, who did not feel safe traveling with route guidance provided by the devices alone, judged it impossible to reach the destination without the assistance of a human guide. They advised that they did not rely fully on announcements, finding them sometimes confusing, especially at the roundabout, with its complex layout, which was difficult to negotiate. Despite the additional information provided by the electronic travel aids, the participants stressed that it is important to stay alert and to be attentive to the layout of the route, which they had to explore with the assistance of a dog guide or long cane, and the course and texture of foot and cycle paths, roads, intersections, and crosswalks. The weak points the participants listed were no announcement of crossing places and the limited accuracy of instructions on turns, which were not always provided exactly at the time and place when and where they should happen. At present, navigation systems are based on road maps. The participants said they would find it desirable if the systems were more customized to the specific needs of pedestrians, including foot and cycle paths, street crossings, and bus and train stations, since they viewed information on public transportation to be a useful addition.
The participants evaluated the "where am I" function as "very useful" and handy. The majority anticipated using this function even on familiar routes for confirmation or to orient or reorient themselves. However, their thoughts differed about points of interest: While some participants deemed them "very useful," often missed in daily life, others thought that they would not make use of this function often and thus that it provided superfluous information.
Announcements of the arrival destination were provided at different locations, depending on the kind of destination, street address or self-created and, in the first case, on the position of the address number on the digital map not necessarily corresponding with an entrance. The starting point and destination derived from a recorded GPS position appeared to be more accurate. The option to reverse a route was perceived as handy and easy.
The participants attached great importance to portability, favoring devices that were as small and lightweight as possible combined with additional functionalities. For outdoor audibility, they said that they would prefer an external speaker over the earphones, easy adjustment of the volume, and an easy repeat function.
With each device, some users were "quite satisfied" to "very satisfied" with its effectiveness. The perceived added value of the devices that were judged as being most functional was specified as decreased dependence on asking other pedestrians for wayfinding information and more independent wayfinding performance. The participants assumed that they would (dare to) travel more and different routes, leading to an increased radius of action, but that they would also use the device on familiar routes for confirmation of their current location and reorientation and for providing a more complete picture of the environment. To some, the combination of a device with a dog guide appeared especially useful. Changes in attitude toward independent travel involved feeling safer, more relaxed, and more self-assured and self-reliant. The participants reported that they needed less effort to concentrate on wayfinding when using the device and that the effort needed to operate and use the device was justified by the functional gain. One participant pointed out that the frequency of use would not be guiding their decision to obtain a navigation system, since even the incidental added value or functional gain would be beneficial. Another participant evaluated the added value of the navigation systems as insufficient at this time.
The participants approved of the two different ways to explore a route in advance provided by the BrailleNote GPS: detailed with all waypoints or turn instructions only, leading to longer execution times for this task. Some thought that the additional braille output was especially useful (particularly the participant with Usher syndrome), and one mentioned the high contrast of the keyboard. The participants described the operation, data entry, and audibility of the device when used indoors positioned on a table as good, but more difficult outdoors when the device was hanging. On two afternoons, BrailleNote gave evidence of serious problems with GPS reception, making its use less reliable, but the participants noted positively, that it recovered well after reestablishing the GPS fix and continued route guidance. Two major points of criticism were the limited portability (heavy, oversized) and audibility outdoors. The participants criticized the absence of an external speaker (the included headphones were not used), as well as the unfavorable position of the internal speaker when used outdoors, the quality of the speech output, the monotony of the voice, the language (English), and the American pronunciation of Dutch (street) names. These points accounted for a relatively low rating on "follow route" (5.8 [+ or -] 1.2) and the number of participants who were not satisfied with the device's dimensions (n = 3), weight (n = 3), and comfort (n = 3).
The participants viewed the detailed information provided by Trekker favorably, especially on side streets and at which side of the street they were located, so that it was obvious if the street had to be crossed. They perceived the "where am I" function as accurate in relation to the estimated house number. Detracting points were serious problems with the GPS reception on two mornings and, on one morning and one afternoon, more temporary and localized problems, particularly at one intersection, which explained the longer execution times for route following. Occasionally, Trekker announced a wrong position, explicable by the influence of a side street. With regard to its operation, difficulties sometimes occurred while navigating the menu because Trekker interpreted the down arrow as Enter. Some participants needed more attempts to position the personal digital assistant correctly; they found it difficult to put on, some criticized that it had three parts, was connected in an inconvenient way (explaining the longest execution time for "positioning device"), and appeared obtrusive.
The majority of participants found the Trekker Breeze device to be very easy to operate, which was reflected in generally short execution times, and its buttons well designed (different forms, well discernable, high contrast). Some appreciated the possibility of recording a route while walking, with features such as turn instructions and street names added automatically. The participants liked the detailed information, especially on side streets and on which side of the street they were located, so that it was obvious if they had to cross over. While some favored that points of interest were provided on the current street segment only, without the possibility to expand, others disapproved, leading to a relatively low rating for "points of interest" (6.4 [+ or -] 1.4).
The main point of criticism, causing the lowest rating for "enter route" (5.1 _ 1.7), was that it is not possible to let a route be automatically created. Most participants considered this function essential. With this device, assistance with creating routes is needed, although in their view a navigation system should foster independence. Negative aspects were that in eight of nine trials, Trekker Breeze provided one incorrect turn instruction at one side street on the way back; that there was a delay in turn instructions at some intersections because of verbosity; and one occasion of temporary, localized problems with the GPS reception at one intersection. Most of the participants (n -7) were satisfied with the effectiveness of Trekker Breeze, defining it as doing what it is designed to do.
The participants liked that preannouncements of the following turn were provided several times at various distances by the Wayfinder Access. High portability, good audibility, and the quality of the voice were mentioned as advantages. The participants' views varied on the route guidance of Wayfinder Access: although some appreciated that it was done in a quieter way, with the possibility of obtaining additional information on request, others criticized the way in which the information was provided. The same was stated for the fact that the information that was provided was less detailed; the name of the street on which they walked and the side streets they encountered were not automatically announced; and information on "where am I" was confined to the street name without the house number.
The disadvantages the participants named were that it was not possible to adjust the distance within points of interest that were searched, that the route could not be reversed directly, and that it was difficult to operate the on-off switch of the mobile phone, leading to longer execution times for this task. All nine participants were "very satisfied" with the dimension, weight, adjustment, and simplicity of the Wayfinder Access, as ascertained by the D-Quest. When asked which device they would judge best or found most useful in a functional sense, five participants named Trekker, five named Wayfinder Access, four named Braille Note, three named Trekker Breeze, and two had no distinct preference for one of the two devices they tested.
In general, the participants can be divided into two groups. One group had in common that the navigation systems did not fully meet their needs and expectations. The main points of critique were that the navigation systems are not yet fully tailored to the needs of pedestrians who are visually impaired because they do not provide announcements of crossing places and are not based on foot- and cycle paths, for example. The limited accuracy of the turn instructions and the "roughness" of the information provided were regarded as insufficient.
The second group found the tested navigation systems useful tools for covering a route in an unfamiliar area. The majority had experienced some form of independent travel on unknown routes before they used the systems and reported various ways in which they did so (such as using voice-recorded instructions). These participants can be described generally as more ready to use a navigation system, more experienced, and as probably having more advanced O&M skills.
Another noticeable finding was the markedly individual preferences expressed regarding the devices' interfaces and the quantity and detail of information (verbosity) that were provided. In this regard, it should be noted that all the devices are adjustable to various extents, so that they can be tailored to the specific needs or preferences of the individual user, and there are different ways to perform a certain task (such as using short keys or key combinations or a menu), which could also have alleviated some of the disadvantages the participants expressed. When one compares the sum of the ratings provided for the tested functionalities and the overall ratings, which are consistent for all devices except the BrailleNote, one can conclude that the navigation systems' portability and outdoor audibility played an important role in the overall evaluation.
One limitation of the study was in the short period of instruction and training, which was confined to the operation of the devices. This limited training was partly contrary to the requirement of using the devices as independently as possible. Because of the difficulty of the outdoor route with regard to the roundabout and no controlled street crossings, it was not possible to let the participants perform all the tasks completely independently. Assistance was also offered for problem solving (such as in situations with poor GPS reception or no GPS fix), since problem solving was not part of the training. An important remark concerning measurement of the amount of time required to perform a task is that the fastest manner was not selected; instead, the one intended to provide quick insights into the operation, options, and the menu structure was chosen. Moreover, the participants were not instructed to perform the tasks as fast as possible, and if they explored a different manner of performing a task, this exploration was not inhibited.
Regarding the aforementioned limitations, it was difficult to generate data that are open to objective assessment. The participants' performance depended on their individual O&M skills, and the functioning of the devices was not always reliable, primarily because of problems with GPS reception, the causes of which were not obvious because they appeared in various weather conditions and at different times of the day, but in free view of the sky. Another point is that not every participant tested all the navigation systems, which can be assumed to have influenced the comparison and overall evaluation of the devices, so that there is a limited comparability of the devices. Finally, a more explorative and qualitative approach was chosen. The participants were a heterogeneous group, but had in common that they were smiled computer users.
Given the complexity and multiple options of the devices and of the route-following task, the results of the study provide insights into the initial use of this kind of assistive technology. Further research should focus on the effects of the long-term use of the devices.
The aim of the study was not to compare and select the best device (and, obviously, there is no "best device"), but to gain insights into a broad range of functionality, provided by different kinds of available systems, as well as to assess their usability. In general, the participants assigned high ratings for the tested functionalities and overall evaluation of the devices, and the majority of the devices' characteristics scored well on the participants' satisfaction, rated by the D-Quest. All the tested navigation systems were found to provide the participants with handy functionalities, judged as added value. On a group level, the results show the advantages and disadvantages of the tested devices, problems and experienced difficulties, and the priority of the features. On an individual level, the participants expressed distinct preferences for various aspects of the devices regarding their usability and diverging perceptions on functional gains, which were closely linked to their O&M and computer skills, prior experiences gained in independent mobility and travel, and their knowledge and expectations of the devices' functional abilities.
These findings stress the importance of careful selection of the most suitable device for the individual user. In addition to a good match between human- and product-related intended use, the context of the selection of assistive technology should be considered, since the different types of hardware can provide a user with the additional functionality of a notetaker or mobile phone.
The method described here was adopted for the assessment of the initial use of the navigation systems, taking into account performance, usability, and subjective evaluation as perceived added value and satisfaction. In this context, the method demonstrated its ability to show differences and generate meaningful results, but could also serve as a useful tool within the advisory process of selecting assistive technology.
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Table 1 Overview of the features of the navigation systems used in the study. Feature BrailleNote Trekker Hardware Specific Dell Axim X51 PDA, notetaker: made accessible BrailleNote through a specific mPower QT v.8 keypad GPS receiver HOLUX M-1000 Globalsat BT-338 Software Sendero GPS 6.0 Trekker 3.0 Map Tele Atlas; SD- Navteq; SD-card Input card QWERTY Braille (six keys are keyboard defined as the dots of a braille letter [SMS-style is possible alternatively]) Output Speech or sound Speech or sound 18-cell External speaker refreshable braille display, built- in speaker Feature Trekker Breeze Wayfinder Access Hardware All-in-one Cell phone: Nokia stand-alone E51, made product accessible through text-to speech application, talks (Nuance) GPS receiver Built in HOLUX M-1000 Software Trekker Breeze 1.0 Wayfinder Access 1.24 Map Navteq; SD- Tele Atlas; Internet Input card Nine Cell phone different keyboard, SMS buttons, wheel style volume adjustment; routes have to be recorded Output Speech or sound Speech or sound External Built-in speaker speaker Table 2 Test situations. Task BrailleNote Trekker Trekker Breeze Switch on and Slide switch, Button, GPS Slide switch on off GPS receiver, receiver, slide Trekker Breeze rocker switch switch, on, BrailleNote external + navigate menu speaker Button on Trekker, + navigate menu Create route Current Address to Starting point (data entry) position to address (a) to destination address (a) (First letter (self- (QWERTY; "full braille + lists created); text") menus) (recorded) Explore route Navigate Navigate Navigate in advance through through through detailed intersection intersection waypoints or information and information and turns only turn turn instructions instructions Positioning Keystroke Navigate menu + One button + Select or commands + list, saved navigate list activate route navigate list routes of saved routes of saved routes Follow route: Keystroke One button One button Where am I? commands What is around Keystroke One button, on One button, on me: Points of commands, current street current street interest within a segment, segment quarter-mile possible to radius, expand (0.5, 1, possible to 2.5 or 5 expand (1, 2, kilometers), 5, or 10 details miles), details (including telephone number) Arrive near Activate route, Activate route, Activate route, destination reverse reverse reverse Create way back Wayfinder Task Access Switch on and Slide switch on off GPS receiver button, mobile phone, + navigate menu Create route Address to (data entry) address (a)(SMS- style; "full text") Explore route Automatically in advance announced "play route" (manually navigating also possible) Positioning Navigate menu + Select or list of saved activate route routes Follow route: Number key Where am I? What is around Number key, in me: Points of the vicinity interest (set radius), details (including telephone number) Arrive near Enter destination destination, Create way "navigate to" back (a) Selected from different possibilities.
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