@article{GDZPPN002319683,
title = {A Cuspidal Class Number Formula for the Modular Curves X1(N).},
journal = {Mathematische Annalen},
volume = {250},
year = {1980},
pages = {197-216},
zbl = {0426.12003},
url = {http://dml.mathdoc.fr/item/GDZPPN002319683}
}
Yu, Jing. A Cuspidal Class Number Formula for the Modular Curves X1(N).. Mathematische Annalen, Tome 250 (1980) pp. 197-216. http://gdmltest.u-ga.fr/item/GDZPPN002319683/