§*H**2*** Space:** a (closed) subspace of *L**2*(*j*R) with functions *F(s)* analytic in *Re(s)* > 0.

§*H**2***^**** Space**: the orthogonal complement of *H**2* in *L**2*, i.e., the (closed) subspace of functions in *L**2* that
are analytic in *Re(s)<*0.

§*Parseval’s relations***: **(between time domain and
frequency domain)