1. R. W. Burch: A Peircean Reduction Theses: The Foundations of Topological Logic. Texas Tech University Press, 1991.
2. LNAI;F. Dau,2000
3. LNAI;F. Dau,2001
4. F. Dau, Negations in Concept Graphs. PhD-Thesis. To appear. Draft on
http://www.tu-darmstadt.de/mathematik/~dau/
5. E. M. Hammer, Logic and Visual Information. CSLI Publications, Stanford, California, 1995.