@incollection{HKS05,
	Author = {F. Havet and R. J. Kang and J.-S. Sereni},
	Booktitle = {{P}roceedings of the 7th {I}nternational {C}onference on {G}raph {T}heory ({I}{C}{G}{T}'05)},
	Doi = {10.1016/j.endm.2005.06.022},
	Pages = {123--128},
	Publisher = {Elsevier},
	Series = {Electron. Notes Discrete Math.},
	Title = {Improper Colourings of Unit Disk Graphs},
	Url = {http://dx.doi.org/10.1016/j.endm.2005.06.022},
	Volume = {22},
	Year = {2005}}