MEDLINE Databank Sources
MEDLINE citations may carry the databank names listed below. These names appear in the DataBankName element in the XML version of the citation; that element is called the Secondary Source ID [SI] element in PubMed for search and display, and is in both the Abstract and MEDLINE displays.
To search for the presence of an SI value on a citation in PubMed, regardless of the specific value, use:
More information on the Secondary Source (SI) field is available at: https://www.nlm.nih.gov/bsd/mms/medlineelements.html#si