The List of Serials Indexed for Online Users (LSIOU) provides bibliographic information for all journals whose articles were ever indexed over time with the MeSH(R) vocabulary and cited in MEDLINE(R), the backbone of the NLM PubMed(R) database. It includes titles that ceased publication, changed titles, or are no longer indexed. More detailed bibliographic data and information about indexing coverage for serials cited in MEDLINE/PubMed can be found in LocatorPlus(R), the NLM online catalog, and the NLM Catalog, an Entrez database.