Remarks

This attribute should be used, when possible, to identify citations that point unambiguously to a particular type of publication, such as a book or a journal.

• If the reference type for the citation is ambiguous, the value “unknown” should be used.
• If the type is quite clear, but the publication category is not in the list below (for example a “personal communication”), the value “other” should be used.

These attribute values can be used, for example, to filter out citations that will not be found in a particular linking service (e.g., no “book”s will be found in PubMed).