@article{GDZPPN00233089X,
title = {Elementary Contractions of Gorenstein Threefolds.},
journal = {Mathematische Annalen},
volume = {280},
year = {1988},
pages = {521-526},
zbl = {0616.14003},
url = {http://dml.mathdoc.fr/item/GDZPPN00233089X}
}
Cutkosky, Steven. Elementary Contractions of Gorenstein Threefolds.. Mathematische Annalen, Tome 280 (1988) pp. 521-526. http://gdmltest.u-ga.fr/item/GDZPPN00233089X/