@article{CMH_1988__63_4_140135,
     author = {Kay Wingberg},
     title = {A {Riemann-Hurwitz} formula for the {Selmer} group of an elliptic curve with complex multiplication.},
     journal = {Commentarii mathematici Helvetici},
     pages = {587--592},
     publisher = {mathdoc},
     volume = {63},
     number = {4},
     year = {1988},
     zbl = {0682.12006},
     url = {http://geodesic.mathdoc.fr/item/CMH_1988__63_4_140135/}
}