@article{MZ_1990__204_3_183781,
     author = {Volker Krafft and Dietmar Osenberg},
     title = {Eisensteinreihen f\"ur einige arithmetisch definierte {Untergruppen} von {SL2} {(IH).}},
     journal = {Mathematische Zeitschrift},
     pages = {425--450},
     publisher = {mathdoc},
     volume = {204},
     number = {3},
     year = {1990},
     zbl = {0725.11024},
     url = {http://geodesic.mathdoc.fr/item/MZ_1990__204_3_183781/}
}