. . "Kostochka, Alexandr V." . "Dvo\u0159\u00E1k, Zden\u011Bk" . "41" . "1"^^ . "By the Grunbaum-Aksenov Theorem (extending Grotzsch's Theorem) every planar graph with at most three triangles is 3-colorable. However, there are infinitely many planar 4-critical graphs with exactly four triangles. We describe all such graphs. This answers a question of Erdos from 1990." . . "10.1016/j.ejc.2014.03.009" . "Planar 4-critical graphs with four triangles" . "European Journal of Combinatorics" . "14"^^ . . . . "Borodin, Oleg V." . "5"^^ . "36734" . . . "11320" . "http://dx.doi.org/10.1016/j.ejc.2014.03.009" . "Yancey, Matthew" . . . "RIV/00216208:11320/14:10283294!RIV15-MSM-11320___" . "triangles; four; with; graphs; 4-critical; Planar"@en . "RIV/00216208:11320/14:10283294" . "0195-6698" . . "P(GBP202/12/G061), P(LH12095)" . "Planar 4-critical graphs with four triangles" . . . "[6E8687DF41ED]" . "\u0159\u00EDjen" . . "000338399000009" . . . . "Planar 4-critical graphs with four triangles"@en . "Lidicky, Bernard" . "By the Grunbaum-Aksenov Theorem (extending Grotzsch's Theorem) every planar graph with at most three triangles is 3-colorable. However, there are infinitely many planar 4-critical graphs with exactly four triangles. We describe all such graphs. This answers a question of Erdos from 1990."@en . "Planar 4-critical graphs with four triangles"@en . . . "GB - Spojen\u00E9 kr\u00E1lovstv\u00ED Velk\u00E9 Brit\u00E1nie a Severn\u00EDho Irska" .