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Documents are deleted for one or more of the following reasons:

1) The document was verified as a duplicate document.

2) The NLM Indexing staff determined the document was "non-indexable" material. The following are a few examples of "non-indexable" material: book reviews, advertisements, announcements, erratum notices, society calendars, software and equipment reviews, papers to appear in forthcoming issues, forwards, table of contents, and documents for articles *not* printed/published in full. Short reports, news items, letters and editorials are also subject to deletion.

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