1. Baader, F.: Terminological cycles in a description logic with existential restrictions. In: Proc. of the 18th Int. Joint Conf. on Artificial Intelligence (IJCAI 2003), pp. 325–330. Morgan Kaufmann, Los Alamitos (2003)
2. Baader, F., Binh, N.T., Borgwardt, S., Morawska, B.: Unification in the description logic $\mathcal{EL}$ without the top concept. LTCS-Report 11-01, TU Dresden, Dresden, Germany (2011), http://lat.inf.tu-dresden.de/research/reports.html
3. Baader, F., Brandt, S., Lutz, C.: Pushing the $\mathcal{EL}$ envelope. In: Proc. of the 19th Int. Joint Conf. on Artificial Intelligence (IJCAI 2005), pp. 364–369. Morgan Kaufmann, Los Alamitos (2005)
4. Baader, F., Calvanese, D., McGuinness, D., Nardi, D., Patel-Schneider, P.F. (eds.): The Description Logic Handbook: Theory, Implementation, and Applications. Cambridge University Press, Cambridge (2003)
5. Lecture Notes in Computer Science;F. Baader,2009