Frédéric Havet Jan van den Heuvel Colin McDiarmid Bruce A. Reed List Colouring Squares of Planar Graphs. 515-519 2007 29 Electronic Notes in Discrete Mathematics http://dx.doi.org/10.1016/j.endm.2007.07.079 db/journals/endm/endm29.html#HavetHMR07