http://pomka.blogspot.com/2008/01/vpn-pptp-centos-5.html
http://pomka.blogspot.com/2008/02/microsoft.html
http://pomka.blogspot.com/2008/07/pptp.html
http://www.opennet.ru/opennews/art.shtml?num=22618
http://www.opennet.ru/opennews/art.shtml?num=22623
http://www.opennet.ru/opennews/art.shtml?num=22619
http://www.opennet.ru/opennews/art.shtml?num=22616
http://habrahabr.ru/blogs/linux/64640/
http://symmetrica.net/cuneiform-linux/yagf-ru.html#download