When citing applicable papers in any applications, proposals, or reports you submit to the NIH, you must include the PubMed Central ID number (NOT the PubMed ID #)
More than 3 months after publication
Less than 3 months after publication or in-press
Note: This applies to articles for which you are either the PI of the NIH award or an author of the article. It does not apply to article you cite but have no affiliation with.