🌐EnglishEnglishDeutschEspañolFrançaisPolskiPortuguêsРусский中文日本語EntityQ1383936· pop 12· linked from 23 articlesHadwiger–Nelson problemmathematical problemAvailable in 12 languagesEspañolFrançaisDeutsch中文РусскийPortuguêsCatalanHebrewHungarianPolskiConnectionsPolymath projectEntityInternational Standard Book NumberEntityCategoriesGeometric graph theoryGraph coloringInfinite graphsMathematical problemsUnsolved problems in graph theory