1. Graphes et Hypergraphes;Berge,1974
2. U.S.R. Murty, Graph Theory with Applications;Bondy,1976
3. Graphs, Groups and Surfaces;White,1973
4. The Four-Color Problem;Ore,1967
5. G. Haggard Edmonds Characterization of Disc Embeddings, in: Proceedings of the 8th Southeastern Conference on Combinatorics, Graph Theory, and Computing, Utilitas Mathematica, Winnipeg, 1977, p. 291–302.