P. Singer, T. Niebler, M. Strohmaier, and A. Hotho. Proceedings of the 22nd international conference on World Wide Web companion, page 171--172. Republic and Canton of Geneva, Switzerland, International World Wide Web Conferences Steering Committee, (2013)
M. Strube, and S. Ponzetto. Proceedings of the National Conference on Artificial Intelligence, 21, page 1419. Menlo Park, CA; Cambridge, MA; London; AAAI Press; MIT Press; 1999, (2006)