@article{MAN_1982__260_163672,
     author = {G. van der Geer},
     title = {On the {Geometry} of a {Siegel} {Modular} {Threefold.}},
     journal = {Mathematische Annalen},
     pages = {317--350},
     year = {1982},
     volume = {260},
     zbl = {0473.14017},
     url = {http://geodesic.mathdoc.fr/item/MAN_1982__260_163672/}
}