1. Perturbation of the continuous spectrum and unitary equivalence;Rosenblum;Pacific J. Math.,1957
2. Perturbations of continuous spectra by trace class operators;Kato,1957
3. Canonical models in quantum scattering theory;de Branges,1966
4. Perturbations of self-adjoint transformations;de Branges;Amer. J. Math.,1962
5. A stationary approach in the abstract theory of scattering;Birman;Izv. Akad. Nauk SSSR,1967