@article{MAN_1995__303_4_165385,
     author = {Peter Hertling},
     title = {Small spanning sets of cusp forms.},
     journal = {Mathematische Annalen},
     pages = {629--652},
     year = {1995},
     volume = {303},
     number = {4},
     zbl = {0834.11020},
     url = {http://geodesic.mathdoc.fr/item/MAN_1995__303_4_165385/}
}