1. The colour numbers of complete graphs;Behzad;J. London Math. Soc.,1967
2. Graph theory;Harary,1969
3. Verallgemeinerte Farbenzahlen;Izbicki,1968
4. The chromatic class and location of a graph on a closed surface;Mel'nikov;Mat. Zametki,1970
5. A six-colour problem on the sphere;Ringel,1968