Geometrization of 3-dimensional orbifolds

This paper is devoted to the proof of the orbifold theorem: If Ο is a compact connected orientable irreducible and topologically atoroidal 3-orbifold with nonempty ramification locus, then Ο is geometric (i.e. has a metric of constant curvature or is Seifert fibred). As a corollary, any smooth orientation-preserving nonfree finite group action on S3 is conjugate to an orthogonal action.