@article{GDZPPN00231858X,
title = {Partial Differential Operators and Discrete Subgroups of a Lie Group.},
journal = {Mathematische Annalen},
volume = {250},
year = {1980},
pages = {101-110},
zbl = {0433.22010},
url = {http://dml.mathdoc.fr/item/GDZPPN00231858X}
}
Jorgensen, Palle E.T. Partial Differential Operators and Discrete Subgroups of a Lie Group.. Mathematische Annalen, Tome 250 (1980) pp. 101-110. http://gdmltest.u-ga.fr/item/GDZPPN00231858X/