DOI and PMID refer to unique identifiers, which can be used to locate articles online. ... The DOI lookup links to any online access we have. PMID is a unique identifier used in the PubMed database and can be used to look up abstracts in PubMed. The PMID lookup links to online access through the library.
10.1186/s12898-019-0263-7 (PDF and Article Link available)
10.1016/j.fas.2020.05.008 (PDF and Article Link available)