1. Baader, F., Brandt, S., Lutz, C.: Pushing the
$$\cal EL$$
envelope. In Proceedings of IJCAI 2005. Morgan-Kaufmann Publishers (2005)
2. Baader, F., Calvanese, D., McGuinness, D.L., Nardi, D., Patel-Schneider, P.F. (eds.): The description logic handbook: theory, implementation, and applications. Cambridge University Press, New York (2007)
3. Ecke, A., Ludwig, M., Walther, D.: The concept difference for
$$\cal EL$$
-terminologies using hypergraphs. In: Proceedings of DChanges 2013. CEUR-WS.org (2013)
4. Grau, B.C., Horrocks, I., Kazakov, Y., Sattler, U.: Modular reuse of ontologies: theory and practice. JAIR 31, 273–318 (2008)
5. Konev, B., Ludwig, M., Walther, D., Wolter, F.: The logical difference for the lightweight description logic
$$\cal EL$$
. JAIR 44, 633–708 (2012)