and

It is shown that if (M,φ, α) is a W∗-dynamical system with M a type I von Neumann algebra then the entropy of α w.r.t. φ equals the entropy of the restriction of α to the center of M. If furthermore (N,ψ, β) is a W∗-dynamical system with N injective then hφ⊗ψ(α ⊗ β) = hφ(α) + hψ(β).