This is about the “National Library of Medicine (grant proposals with PMCID/PMID)” style. I’ve gotten feedback that this style is including URLs in references (usually in the form of “Available from: htttp”//…") URLs are forbidden in NIH grant applications. I’ve been removing them manually. Just a heads up so nobody has their grant auto-rejected. Perhaps this style could be modified or another sub-style created?
Thank you for sharing this information about this citation style @Bill_Jackson. We get our styles from citationstyles.org. You could try modifying the “National Library of Medicine (grant proposals with PMCID/PMID)” style manually using citation style editor available at editor.citationstyles.org. There you can search for citation styles and modify existing styles to your needs (see here and here for more information).