What is a publication type? How does it differ from descriptors?
Since 1991, Publication Types have been assigned by NLM indexers to describe the form of presentation of materials that are indexed. Some PTs reflect the format and editorial practices of the individual journal; others reflect the indexer’s analytical judgment. Items indexed prior to 1991 have had a limited number of PTs added by machine rather than by re-indexing. Publication Types such as “letter” or “editorial” are determined by the style or section heading used by the journal. “Letter” is assigned both to routine letters to the editor as well as to lengthier articles if the journal labels them as “scientific correspondence” or similar caption. Likewise, some journals label lead articles as “editorial,” while others reserve this caption for expressions of opinion. NLM follows the journal’s practice, and assigns the Publication Type “editorial” rather than “journal article” in both these cases. A “classical article” is one that has been reprinted by a journal because of its significa
