@article{MM2_1987__59_155259,
     author = {Ulrich Christian},
     title = {\"Uber gewisse {Poincar\'e'sche} {Reihen} zu elliptischen {Modulgruppen.}},
     journal = {Manuscripta mathematica},
     pages = {423--440},
     publisher = {mathdoc},
     volume = {59},
     year = {1987},
     zbl = {0627.10016},
     url = {http://geodesic.mathdoc.fr/item/MM2_1987__59_155259/}
}