NIH Guidance:

The "Bibliography & References Cited" attachment is required unless otherwise noted in the FOA.

While there are no page limitations, it is important to be concise and to select only those literature references pertinent to the proposed research.

• NIH Application Guide - Bibliography/References
• Frequently Asked Questions - Citing Interim Research Products

Content:

The references should be limited to relevant and current literature.

The "Bibliography & References Cited" attachment should include any references cited in G.400 - PHS 398 Research Plan Form and in the G.500 - PHS Human Subjects and Clinical Trials Information form

The NIH does not require a specific format for the citations, however the PubMed Central reference number (e.g., PMCID#1234567) or the NIH Manuscript Submission reference number (e.g., NIHMS#97531) is required to be included for each of the following citations:

1. Articles that fall under the Public Access Policy, (i.e. they were authored or co-authored by the applicant, arose from NIH support, were peer-reviewed, and accepted for publication on or after April 7, 2008)
   
   
2. Articles that were authored or co-authored by the applicant and arose from AHRQ funding provided after February 19, 2016

If the PMCID is not yet available because the Journal submits articles directly to PMC on behalf of their authors, indicate "PMC Journal - In Process." NIH maintains a list of such journals. 

Citations that are not covered by the Public Access Policy, but are publicly available in a free, online format may include URLs or PubMed ID (PMID) numbers along with the full reference.

You are also allowed to cite interim research products although they do have specific citation requirements. See the Frequently Asked Questions link above for more information.