Reduction algorithms for some classes of aperiodic monoids Roman König — 1985 RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications
Finite hull systems and their implication bases. (Endliche Hüllensysteme und ihre Implikationenbasen.) König, Roman — 2002 Séminaire Lotharingien de Combinatoire [electronic only]