1. Dvorak Z., Kral’ D., Nejedly P., and Skrekovski R., “Coloring squares of planar graphs with girth six,” European J. Combin., 29, No. 4, 838–849 (2008).
2. Borodin O. V., Broersma H. J., Glebov A. N., and van den Heuvel J., “The minimum degree and chromatic number of the square of a planar graph,” Diskret. Anal. Issled. Oper., 8, No. 4, 9–33 (2001).
3. Borodin O. V., Ivanova A. O., and Neustroeva T. K., “(p, q)-coloring of sparse planar graphs,” Mat. Zametki YaGU, 13, No. 2, 3–9 (2006).
4. Borodin O. V., Ivanova A. O., and Neustroeva T. K., “List (p, q)-coloring of sparse planar graphs,” Sibirsk. Elektron. Mat. Izv., 3, 355–361 (2006) ( http://semr.math. nsc.ru ).
5. Wegner G., Graphs with Given Diameter and a Coloring Problem, Technical Report. Univ. of Dortmund, Germany (1977).