1. [1] G. B. Folland and E. M. Stein, Hardy Spaces on Homogeneous Groups, Mathematical Notes, vol. 28, Princeton University Press, Princeton, N.J., 1982.
2. [2] Harish-Chandra, Spherical functions on a semisimple Lie group. I, Amer. J. Math. 80 (1958), 241–310.
3. [3] F. I. Karpelevič, The geometry of geodesics and the eigenfunctions of the Beltrami-Laplace operator on symmetric spaces, Trudy Moskov. Mat. Obšč. 14 (1965), 48–185, Engl. Transl. in Trans. Moscow Math. Soc. 1965, 51–199, Amer. Math. Soc., Providence, R.I. 1967.
4. [4] A. Koranyi, Harmonic functions on symmetric spaces, Symmetric spaces (Short Courses, Washington Univ., St. Louis, Mo., 1969–1970) eds. W. Boothby and G. Weiss, Dekker, New York, 1972, 379–412. Pure and Appl. Math., Vol. 8.
5. [5] A. Korányi, A survey of harmonic functions on symmetric spaces, Harmonic analysis in Euclidean spaces (Proc. Sympos. Pure Math., Williams Coll., Williamstown, Mass., 1978), Part 1, Proc. Sympos. Pure Math., XXXV, Part, Amer. Math. Soc., Providence, R.I., 1979, pp. 323–344.