Geodesic
On the nonexistence of 4-critical graphs of twelfth order
Diskretnaya Matematika, Tome 4 (1992) no. 2, pp. 99-114 
G. P. Gavrilov; I. A. Muzychuk. On the nonexistence of 4-critical graphs of twelfth order. Diskretnaya Matematika, Tome 4 (1992) no. 2, pp. 99-114. http://geodesic.mathdoc.fr/item/DM_1992_4_2_a11/
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     title = {On the nonexistence of 4-critical graphs of twelfth order},
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Voir la notice de l'article provenant de la source Math-Net.Ru

The question of the existence of 4-critical (with respect to the edge coloring) graphs with 12 vertices is investigated. It has been proved that such graphs do not exist.