@article{IM_1988__91_3_143542,
     author = {N.I. Shepherd-Barron and J. Koll\'ar},
     title = {Threefolds and deformations of surface singularities.},
     journal = {Inventiones mathematicae},
     pages = {299--338},
     year = {1988},
     volume = {91},
     number = {3},
     zbl = {0642.14008},
     url = {http://geodesic.mathdoc.fr/item/IM_1988__91_3_143542/}
}