1. Bollobás, B.: Extremal Graph Theory. Academic Press, London (1978)
2. Diestel, R.: Graph Theory. Springer, New York (1997)
3. Distel, R.: Graph Theory Electronic Edition (2000)
4. Dvorak, Z., Lidicky, B., Mohar, B.: 5-choosability of graphs with crossings far apart. Combinatorics (2012)
5. Eaton, N., Hull, T.: Defective List Colorings of Planar Graphs. Bull Inst. Combin., Appl. 25, 79–87 (1999)