@article{GDZPPN00233609X,
title = {Extremal rays on higher dimensional projective varieties.},
journal = {Mathematische Annalen},
volume = {291},
year = {1991},
pages = {497-504},
zbl = {0762.14009},
url = {http://dml.mathdoc.fr/item/GDZPPN00233609X}
}
Zhang, Qi. Extremal rays on higher dimensional projective varieties.. Mathematische Annalen, Tome 291 (1991) pp. 497-504. http://gdmltest.u-ga.fr/item/GDZPPN00233609X/