1. Zhelobenko, D.P.: Izv. AN SSSR, Ser. Mat.,32, 108 (1968); in Russian.
2. Gel'fand, I.M., Graev, M.I., Vilenkin, N.Ya.: Generalized functions, vol. 5. Integral geometry and representation theory; Chap. III. New York: Academic Press 1966.
3. Naimark, M.A.: Trudy Moskov. Matem. Obsčestava,8, 121 (1959); in Russian. English translation: Am. Math. Soc. Transl., Ser. 2,36, 101 (1964).
4. Oksak, A.I.: Teoret. i Matem. Fiz.,12, 179 (1972); in Russian.
5. Schwartz, L.: Théorie des distributions. Paris: Hermann 1950/51.