@book{AST_1974__20__1_0,
     author = {Pinkham, Henry C.},
     title = {Deformations of algebraic varieties with $G_m$ action},
     series = {Ast\'erisque},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {20},
     year = {1974},
     mrnumber = {376672},
     zbl = {0304.14006},
     language = {en},
     url = {http://www.numdam.org/item/AST_1974__20__1_0/}
}