1. Anderson, A.R., Belnap, N., Dunn, J.: Entailment: The Logic of Relevance and Necessity, vol. 1. Princeton University Press (1976)
2. Lecture Notes in Computer Science;C Benzmüller,2015
3. Blackburn, P., de Rijke, M., Venema, Y.: Modal Logic. Cambridge Tracts in TCS 8 (2002)
4. LNM;JA Barmak,2011
5. Baum, J.D.: Elements of Point Set Topology. Dover (1991)