Note that in the general form of the Robertson–Schrödinger uncertainty relation, there is no need to assume that the operators A ^ ^ and B ^ ^ are self-adjoint operators. It suffices to assume that they are merely symmetric operators. (The distinction between these two notions is generally glossed over in the physics literature, where the term Hermitian is used for either or both classes of operators. See Chapter 9 of Hall's book for a detailed discussion of this important but technical distinction.)