@article{bwmeta1.element.bwnjournal-article-aav24i3p313bwm,
author = {Rankin, R.},
title = {Subgroups of the modular group defined by a single linear congruence},
journal = {Acta Arithmetica},
volume = {22},
year = {1973},
pages = {313-323},
zbl = {0273.10016},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-aav24i3p313bwm}
}
Rankin, R. Subgroups of the modular group defined by a single linear congruence. Acta Arithmetica, Tome 22 (1973) pp. 313-323. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-aav24i3p313bwm/