@article{MAN_1980__253_163464,
     author = {Kenneth A. Ribet},
     title = {Twists of {Modular} {Forms} and {Endomorphisms} of {Abelian} {Varieties.}},
     journal = {Mathematische Annalen},
     pages = {43--62},
     publisher = {mathdoc},
     volume = {253},
     year = {1980},
     zbl = {0421.14008},
     url = {http://geodesic.mathdoc.fr/item/MAN_1980__253_163464/}
}