1. N. Alon, M. Tarsi. Colorings and orientations of graphs, Graphs and Combinatorics 1, 115–127, 1985.
2. N. Alon, J. Spencer. The probabilistic Method, Wiley, New York 1992.
3. K. Appel, W. Haken. Every planar map is four colorable, Part 1: Discharging; Part 2: Reducibility. Illinois J. Math. 21, 429–567, 1977.
4. C. Berge. Théorie des graphes et ses applications, Dunod 1958.
5. C. Berge. Färbung von Graphen, deren sämtliche bzw. deren ungerade Kreise star sind, Wiss. z. Martin Luther Univ. Halle-Wittenberg Math. Nature Reihe 10, 114–115, 1961.