@article{GDZPPN002334356,
title = {Unitary spectum and the fundamental group for actions of semisimple Lie groups.},
journal = {Mathematische Annalen},
volume = {287},
year = {1990},
pages = {697-702},
zbl = {0681.22014},
url = {http://dml.mathdoc.fr/item/GDZPPN002334356}
}
Zimmer, Robert J. Unitary spectum and the fundamental group for actions of semisimple Lie groups.. Mathematische Annalen, Tome 287 (1990) pp. 697-702. http://gdmltest.u-ga.fr/item/GDZPPN002334356/