1. Patrick Billingsley, Convergence of Probability Measures, Wiley, New York, 1968.
2. William Feller, An Introduction to Probability Theory and Its Applications, vol. I, 3rd ed., Wiley, New York, 1968.
3. David Freedman, Brownian Motion and Diffusion, Holden-Day, San Francisco, 1971.
4. G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 4th ed., Clarendon Press, Oxford, 1960. /