This test checks if the pathway cites external resources. Each pathway should have at least one reference.
Currently, the GPML only fully supports PubMed identifiers, and the tests throws false positives for pathways with zero PubMed identifiers but with a book, book chapter, or references with only DOIs.
The pathway does not cite a reference with a PubMed identifier.
An additional PubMed identifier can be added to the pathway. This also solves the false positives.