Author/Authors :
Borodin، نويسنده , , Oleg V. and Dvo??k، نويسنده , , Zden?k and Kostochka، نويسنده , , Alexandr V. and Lidick?، نويسنده , , Bernard and Yancey، نويسنده , , Matthew، نويسنده ,
Abstract :
By the Grünbaum–Aksenov Theorem (extending Grötzsch’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 Erdős from 1990.
