@article{1103043969, author = {Reiner, Irving and Swift, J. D.}, title = {Congruence subgroups of matrix groups.}, journal = {Pacific J. Math.}, volume = {6}, number = {4}, year = {1956}, pages = { 529-540}, language = {en}, url = {http://dml.mathdoc.fr/item/1103043969} }
Reiner, Irving; Swift, J. D. Congruence subgroups of matrix groups.. Pacific J. Math., Tome 6 (1956) no. 4, pp. 529-540. http://gdmltest.u-ga.fr/item/1103043969/