@article{DM_1992_4_2_a11,
     author = {G. P. Gavrilov and I. A. Muzychuk},
     title = {On the nonexistence of 4-critical graphs of twelfth order},
     journal = {Diskretnaya Matematika},
     pages = {99--114},
     year = {1992},
     volume = {4},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_1992_4_2_a11/}
}