J. Heflin, и J. Hendler. Proceedings of the Seventeenth National Conference on Artificial Intelligence (AAAI-2000), стр. 443--449. AAAI/MIT Press, Menlo Park, CA, (2000)
M. Klein, D. Fensel, A. Kiryakov, и D. Ognyanov. Proc. of the 13th European Conf. on Knowledge Engineering and Knowledge Management (EKAW02) (Siguenza, Spain), стр. 197--212. (2002)