The uniqueness of the adjoint operation. II

Let H be a complex, finite-dimensional Hilbert space, and let L(H) denote the set of linear transformations mapping H into itself. For certain interesting subsets A(H) of L(H) [nonsingular transformations and L(H) are examples], the functions h: A(H) → L(H) which have the properties h(ST) = h(T)h(S) and h(S)S ⩾ 0 are characterized.