@article{MAN_1973__200_162337,
     author = {William F. Hammond},
     title = {The {Hilbert} {Modular} {Surface} of a {Real} {Quadratic} {Field.}},
     journal = {Mathematische Annalen},
     pages = {25--46},
     publisher = {mathdoc},
     volume = {200},
     year = {1973},
     zbl = {0236.14014},
     url = {http://geodesic.mathdoc.fr/item/MAN_1973__200_162337/}
}