@article{IM2_2016_80_5_a4,
     author = {S. Mori and Yu. G. Prokhorov},
     title = {Threefold extremal contractions of type {(IIA).~I}},
     journal = {Izvestiya. Mathematics},
     pages = {884--909},
     year = {2016},
     volume = {80},
     number = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2016_80_5_a4/}
}