4 - general information about /proc/sys/ sysctl files.
6 - documentation for /proc/sys/abi/*.
8 - explanation of why one should not add new binary sysctl numbers.
10 - documentation for /proc/sys/fs/*.
12 - documentation for /proc/sys/kernel/*.
14 - documentation for /proc/sys/sunrpc/*.
16 - documentation for /proc/sys/vm/*.