http://tttyx2vwp7ihml3vkhywwcizv6nbwrikpgeciy3qrow7l7muak2pnhad.onion/Publications.html
Not even the
public directory servers will know how a private hidden service can
be contacted, or know it exists. "Locating Hidden Servers",
Proceedings of the 2006 IEEE Symposium on Security and Privacy,
IEEE CS Press, Oakland, CA, May 2006.
[ PDF ] Hidden services were deployed on the Tor anonymous communication
network in 2004.