1. I. M. Gel'fand, "Center of infinitesimal group ring," Mat. Sb.,26, 103?112 (1950).
2. I. M. Gel'fand, "Spherical functions on symmetric Riemann spaces," Dokl. Akad. Nauk SSSR,70, No. 1, 5?8 (1950).
3. F. A. Berezin, "Laplace operators on semisimple Lie groups," Tr. Mosk. Mat. Ob-va,6, 371?463 (1957).
4. F. A. Berezin and F. I. Karpelevich, "Zonal spherical functions and Laplace operators on certain symmetric spaces," Dokl. Akad. Nauk SSSR,118, No. 1, 9?12 (1958).
5. M. A. Olshanetsky and A. M. Perelomov, "Completely integrable Hamiltonian systems connected with semisimple Lie algebras," Invent. Math.,37, 93?108 (1976).