@article{bwmeta1.element.bwnjournal-article-aav18i1p145bwm,
author = {Rankin, R.},
title = {Subgroups of the modular group generated by parabolic elements of constant amplitude},
journal = {Acta Arithmetica},
volume = {18},
year = {1971},
pages = {145-151},
zbl = {0218.20046},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-aav18i1p145bwm}
}
Rankin, R. Subgroups of the modular group generated by parabolic elements of constant amplitude. Acta Arithmetica, Tome 18 (1971) pp. 145-151. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-aav18i1p145bwm/