@article{MAN_1976__222_162851,
     author = {Mary Schaps},
     title = {Birational {Morphisms} {Factorizable} by two {Monoidal} {Transformations.}},
     journal = {Mathematische Annalen},
     pages = {23--28},
     publisher = {mathdoc},
     volume = {222},
     year = {1976},
     zbl = {0309.14009},
     url = {http://geodesic.mathdoc.fr/item/MAN_1976__222_162851/}
}