Francesco M. Donini Maurizio Lenzerini Daniele Nardi Werner Nutt Andrea Schaerf An Epistemic Operator for Description Logics. 225-274 1998 100 Artif. Intell. 1-2 db/journals/ai/ai100.html#DoniniLNNS98 http://dx.doi.org/10.1016/S0004-3702(98)00009-5