What is a DOI or PMID ?
DOI stands for Digital Object Identifier. This identifier labels an individual article (like a serial number) in order that a permanent URL can be created. When searching many databases, the article description will often include a DOI:
The first part before the / is the publisher portion of the number. The second part points to the journal and article specifically.
To learn more about DOIs, see: http://www.doi.org
A PubMed Identifier (PMID) is a unique number assigned to each PubMed citation of life sciences and biomedical scientific journal articles:
PubMed identifiers allow you to search within the PubMed database using the PMID to access the article information. You can also search Google by entering PMID and the number (e.g., PMID: 19687089)