POSIX version affects Coreutils

1) http://lists.debian.org/debian-glibc/2003/08/msg00127.html
This has some information about the sort & tail.
2) http://linux.com.hk/PenguinWeb/manpage.jsp?name=sysconf&section=3
This has information on the System Environment Variables
3) http://www.sunsite.ualberta.ca/Documentation/Gnu/gawk-3.0.6/html_node/gawk_136.html#IDX513
This is quite long, about GNU which relates to POSIX variable.