1. Solution of Ringelʼs problem about vertex bound colouring of planar graphs and colouring of 1-planar graphs;Borodin;Metody Diskret. Analiz.,1984
2. Topological Graph Theory;Gross,1987
3. A Classical Introduction to Modern Number Theory;Ireland,1982
4. A lower bound for the one-chromatic number of a surface;Korzhik;J. Combin. Theory Ser. B,1994
5. A tighter bounding interval for the one-chromatic number of a surface;Korzhik;Discrete Math.,1997