1. A. Anjewierden, J. Wielemaker, and C. Toussaint. Shelley-computer aided knowledge engineering. Knowledge Acquisition, 4(1), 1992.
2. G. Booch, J. Rumbaugh, and I. Jacobson. The Unified Modelling Language User Guide. Addison-Wesley, Reading, MA, 1998.
3. V.K. Chaudhri, A. Farquhar, R. Fikes, P.D. Karp, and J.P. Rice. OKBC: A programmatic foundation for knowledge base interoperability. In Proceedings 15th National Conference on Artificial Intelligence (AAAI-98). Madison, Wisconsin. AAAI Press/MIT Press, 1998.
4. O. Corby and R. Dieng. The WebCokace knowledge server. IEEE Internet Computing, 3(6):38–43, November/December 1999.
5. N. Fridman Noy, R.W. Fergerson, and M. A. Musen. The knowledge model of Protégé-2000: combining interoperability and flexibility. In Proceedings of EKAW’2000. Springer-Verlag, 2000. This volume. Also as: Technical Report Stanford University, School of Medicine, SMI-2000-0830.