@article{1250523378, author = {Chuman, Yasuhiro}, title = {Generators and relations of $\Gamma\_0(N)$}, journal = {J. Math. Kyoto Univ.}, volume = {13}, number = {3}, year = {1973}, pages = { 381-390}, language = {en}, url = {http://dml.mathdoc.fr/item/1250523378} }
Chuman, Yasuhiro. Generators and relations of $\Gamma_0(N)$. J. Math. Kyoto Univ., Tome 13 (1973) no. 3, pp. 381-390. http://gdmltest.u-ga.fr/item/1250523378/