The Netgraph Networking System, http://www.elischer.org/netgraph/
The Netgraph user library man page, netgraph(3)
The Netgraph facility man page, netgraph(4)
The ngctl configuration program man page, ngctl(3)
The nghook utility program man page, nghook(3)
DaemonNews Netgraph article, http://www.daemonnews.org/200003/netgraph.html
Netgraph ATM, http://www.fokus.gmd.de/research/cc/cats/employees/hartmut.brandt/ngatm/
