@article{MAN_1990__286_1-3_164639,
     author = {Steven H. Weintraub and Klaus Hulek},
     title = {The principal degenerations of abelian surfaces and their polarisations.},
     journal = {Mathematische Annalen},
     pages = {281--308},
     publisher = {mathdoc},
     volume = {286},
     number = {1-3},
     year = {1990},
     zbl = {0715.14034},
     url = {http://geodesic.mathdoc.fr/item/MAN_1990__286_1-3_164639/}
}