POSIX
http://man7.org/tlpi/api_changes/index.html#posix
POSIX/Single
UNIX
Specification
POSIX.1-2008 Technical Corrigendum 3 (in progress)
POSIX.1-2008 Technical Corrigendum 2 (POSIX.1-2016)
POSIX.1-2008 Technical Corrigendum 1 (POSIX.1-2013)