@article{MAN_1975__214_162679,
     author = {Frans Oort},
     title = {Which {Abelian} {Surfaces} are {Products} of {Elliptic} {Curves} ?},
     journal = {Mathematische Annalen},
     pages = {35--48},
     publisher = {mathdoc},
     volume = {214},
     year = {1975},
     zbl = {0283.14007},
     url = {http://geodesic.mathdoc.fr/item/MAN_1975__214_162679/}
}