Martin Aigner Gianluca De Marco Manuela Montangero The Plurality Problem with Three Colors. 513-521 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2996&spage=513 2004 conf/stacs/2004 STACS db/conf/stacs/stacs2004.html#AignerMM04