PMID (PubMed ID) is the unique identifier for a publication's abstract in PubMed.
PMCID (PubMed Central ID) is the unique identifier for a free complete article (once it is publicly available) in PubMed Central.
PubMed and PubMed Central, produced by the U.S. National Library of Medicine, are text archives of biomedical and life sciences literature.
A DOI (Digital Object Identifier) is a publisher’s unique identifier for a publication. The prefix http://dx.doi.org/ is presumed. Publishers may charge for access.
Lynch P, Wang Y, Kanduru A, Luan X, Mericle L, Lu S, McDonald CJ.On‐the‐Fly Data Capture Tooling for FHIR/HL7 V2 HL7 January 2018 Working Group Meeting, New Orleans, LA February 1st, 2018.
Zarin D, Tse T.Trust but verify: trial registration and determining fidelity to the protocol [Letter]. Ann Intern Med. 2013 Jul 2;159(1):65-7. doi: 10.7326/0003-4819-159-1-201307020-00011.
Zarin D.Factual Errors about ClinicalTrials.gov and other federal mandates in special report by Shuster [Letter]. Clin Transl Sci. 2012 Apr;5(2):217; author reply 217. doi: 10.1111/j.1752-8062.2012.00410.x.