@article{MOMA_1972__76_177607,
     author = {H.G. Helfenstein},
     title = {The {Hurwitz} {Relation} for {Tori.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {300--305},
     publisher = {mathdoc},
     volume = {76},
     year = {1972},
     zbl = {0248.53007},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1972__76_177607/}
}