1. Feller, W. (1966). An Introduction to Probability Theory and. Its Applications, Vol. II. Wiley, New York.
2. Fisher, R. A. (1958). Statistical Methods for Research Workers, 13th ed. Oliver and Boyd, Edinburgh.
3. Gnedenko, B. V. and Kolmogorov, A. N. (1954). Limit Distributions for Sums of Independent Random Variables. Addison- Wesley, Cambridge, Mass.
4. Heyde, C. C. (1963). Quart. J. Math. Oxford 14, 97–105.
5. Heyde, C. C. and Seneta, E. (1972). Biometrika 59, 680–683.