NIST SP 800-38D
NIST's 2007 standard specifying GCM and its authentication-only sibling GMAC.
Published in November 2007, it made McGrew and Viega's Galois/Counter Mode an approved mode of operation for US federal use. It defines both GCM, which encrypts and authenticates, and GMAC, which only authenticates. The recommended IV length is 96 bits; other lengths are allowed but must first be hashed through GHASH, which complicates everything.
The section that matters most is the one on IVs. Random IVs may be used at most 232 times per key, and a repeated IV means authentication collapses entirely. The spec also permits tags as short as 32 bits for special applications — a concession cryptographers have spent fifteen years talking people out of.