1. Bateman, H.: Higher transcendental functions. Vol. II. New York: McGraw Hill 1953.
2. Blackwell, D.: On a class of probability spaces. Proc. 3th Berkeley Sympos. math. Statist. and Probability II, 1?6 (1956).
3. Bochner, S.: Positive zonal functions on spheres. Proc. nat. Acad. Sci. USA 40, 1141 to 1147 (1954).
4. Courant, R., and D. Hilbert: Methods of Mathematical Physics. Vol. 1. New York: Interscience Publishers 1953.
5. Doob, J. L.: Stochastic Processes. New York: J. Wiley and Sons 1953.