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Let be the decomposition into prime cycles. It is enough to prove the claim for the closures of in . We may hence assume that is irreducible and reduced. Furthermore by passing to a dominating model as in 4, we may assume that the special fibre of is reduced. As has no boundary, every irreducible component of is proper by Corollary A.4 and hence using commutativity of the intersection product ([Gub98, Theorem 5.9]) we obtain