1. M. Reed and B. Simon, Methods of Modern Mathematical Physics, Vol. 3, Scattering Theory, Acad. Press, New York (1979).
2. S. M. Tashpulatov, Theor. Math. Phys., 126, 403–408 (2001).
3. M. A. Naimark, Normed Rings [in Russian], Nauka, Moscow (1968); English transl., Wolters-Noordhoff, Groningen (1970).
4. M. Wortis, Phys. Rev., 132, 85–97 (1963).
5. S. M. Tashpulatov, Theor. Math. Phys., 107, 544–549 (1996).