Vlassis Krikos Sofia Stamou Pavlos Kokosis Alexandros Ntoulas Dimitris Christodoulakis DirectoryRank: ordering pages in web directories. 17-22 2005 conf/widm/2005 WIDM http://doi.acm.org/10.1145/1097047.1097052 db/conf/widm/widm2005.html#KrikosSKNC05