In this paper we describe the structure of all sequential isomorphisms
between the sets of von Neumann algebra effects. It turns out that if the
underlying algebras have no commutative direct summands, then every sequential
isomorphism between the sets of their effects extends to the direct sum of a
*-isomorphism and a *-antiisomorphism between the underlying von Neumann
algebras.Comment: To appear in Acta Sci. Math. (Szeged