1. Artificial Intelligence (1984), Vol.24, Numbers 1–3, Special Volume on Qualitative Reasoning about Physical Systems
2. Allen, James F.: Maintaining Knowledge about Temporal Intervals, CACM, Vol.26, No.11, 832–843
3. Blum,Norbert : Fehlererkennung in kombinatorischen Schaltkreisen, SFB 124-B2, Bericht 10/1985, Fachbereich 10 der Universität des Saarlandes, Saarbrücken
4. Charniak, Eugene; McDermott, Drew : Introduction to Artificial Intelligence, Addison Wesley
5. Davis, Randall: Expert Systems: Where are we? and where do we go from here?, AI-Magazine, Spring 1982, pp. 3–22