Steffen Staab Jürgen Angele Stefan Decker Michael Erdmann Andreas Hotho Alexander Maedche Hans-Peter Schnurr Rudi Studer York Sure Semantic community Web portals. 473-491 2000 33 Computer Networks 1-6 db/journals/cn/cn33.html#StaabADEHMSSS00 http://dx.doi.org/10.1016/S1389-1286(00)00039-6