@article{MAT_1971_15_6_a1,
     author = {J.-P. Serre},
     title = {Le probl\`eme des groupes de congruence pour $\mathrm{SL}_2$},
     journal = {Matematika},
     pages = {12--45},
     publisher = {mathdoc},
     volume = {15},
     number = {6},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MAT_1971_15_6_a1/}
}