2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150139We classify extremal divisorial contraction which contracts a divisor to a curve from a smooth fourfold. We prove the exceptional divisor is $\Bbb P^2$bundle or quadric bundle over a smooth curve and the contraction is the blowing up along the curve.Amstex v.2.1, 8 pagesAlgebraic Geometrytext