Alexandr V. Kostochka Jaroslav Nesetril P. Smolíková Colorings and homomorphisms of degenerate and bounded degree graphs. 257-276 2001 233 Discrete Mathematics 1-3 http://dx.doi.org/10.1016/S0012-365X(00)00245-4 db/journals/dm/dm233.html#KostochkaNS01