Let M be a von Neumann algebra, φ be a faithful, normal semifinite weight on M and Mφ its centralizer. We characterize the conditional expectations Eφ : M → Mφ of finite index for a faithful normal ...

Michio Suzuki, Finite Groups in Which the Centralizer of Any Element of Order 2 is 2-Closed, Annals of Mathematics, Vol. 82, No. 1 (Jul., 1965), pp. 191-212 ...