Why am I retrieving MEDLINE (rather than OLDMEDLINE) citations with publication dates prior to 1966?
MEDLINE has always included a small number of records citing articles published prior to 1966 (about 109,000). As of late 2006, the set of records marked with a status of MEDLINE includes OLDMEDLINE records where all of the original subjects have been mapped to current MeSH vocabulary. These OLDMEDLINE records will be retrieved in PubMed when limiting to the MEDLINE® subset by searching medline [sb]. Records that have not yet been completely updated to current MeSH will carry the status tag [PubMed – OLDMEDLINE]. PubMed or Gateway searchers not interested in these older citations are advised to restrict their searches using the date range function within the Limits feature, or to set up a filter for publication date. Searchers can isolate records that originated from the older print indices of the Cumulated Index Medicus (CIM) and the Current List of Medical Literature (CLML) by searching the value jsubsetom. See also the Technical Bulletin article Changes to OLDMEDLINE Records – Statu
