EntityQ1383936· pop 12· linked from 23 articlesHadwiger–Nelson problemSign in to savemathematical problemConnectionsPolymath projectEntityInternational Standard Book NumberEntityset theoryEntitypointEntitydigital object identifierEntityInternational Standard Serial NumberEntityPaul ErdősEntitygraph theoryEntitycurveEntityequilateral triangleEntityJSTOREntitybibcodeEntityQ118398Entityfour color theoremEntityif and only ifEntityMartin GardnerEntityaxiom of choiceEntityScientific AmericanEntitytessellationEntityQ22908627EntityCategoriesGeometric graph theoryGraph coloringInfinite graphsMathematical problemsUnsolved problems in graph theory