1. Anderson, A.R.: The Formal Analysis of Normative Systems. In The Logic of Action and Decision, ed. Rescher, N., Pittsburgh: The University of Pittsburgh Press, 1967
2. Blanchard, M.: Le GRAFCET pour une Representation Normalisee de Cahier des Charges d'un Automatisme Logique. Automatique et Informatique Industrielle, No. 61, pp. 27–32 + No. 62, pp. 36–40 (1977)
3. Best, E.: A Theorem on the Characteristics of Non-Sequential Processes. Computing Laboratory Technical Report No. 116, University of Newcastle-upon-Tyne (1977)
4. Chaney, T.J.; Ornstien, S.M.; Littlefield, W.M.: Beware the Synchronizer. COMPCON-72, IEEE Computer Society Conference, pp. 12–14, 1972
5. Chang, C.; Lee, R.: Symbolic Logic and Mechanical Theorem Proving. New York, London: Academic Press, 1973