@article{CMH_1990__65_3_140203,
     author = {Stephen S.-T. Yau and Anatoly Libgober},
     title = {An obstruction for smoothing of {Gorenstein} surface singularities.},
     journal = {Commentarii mathematici Helvetici},
     pages = {413--433},
     publisher = {mathdoc},
     volume = {65},
     number = {3},
     year = {1990},
     zbl = {0728.14035},
     url = {http://geodesic.mathdoc.fr/item/CMH_1990__65_3_140203/}
}