Threefold extremal contractions of type IA

Shigefumi Mori, Yuri Prokhorov

Let $(X,C)$ be a germ of a threefold $X$ with terminal singularities along an irreducible reduced complete curve $C$ with a contraction $f:(X,C)\to (Z,o)$ such that $C=f^{-1}(o)_{…