NIST Special Publication 800-63-3 - Digital Identity Guidelines 

Offline Documents:

NIST.SP.800-63a.pdf

NIST.SP.800-63b.pdf

NIST.SP.800-63c.pdf

NIST.SP.800-63-3.pdf

Links to the documents: 

Main website: https://pages.nist.gov/800-63-3/

SP 800-63-3 https://pages.nist.gov/800-63-3/sp800-63-3.html

SP 800-63-A https://pages.nist.gov/800-63-3/sp800-63a.html

SP 800-63-B https://pages.nist.gov/800-63-3/sp800-63b.html

SP 800-63-C https://pages.nist.gov/800-63-3/sp800-63c.html