1. Bebbington, M., Lai, C. D., Wellington, M. and Zitikis, R. (2010). Discrete bathtub distributions: Mind the step function,Advanced Reliability Modeling IV: Beyond the Traditional Reliability and Maintainability Approaches, Proceedings 4th Asia-Pacific Symposium (APARM2010), S. Chukova, J. Haywood and T. Dohi (eds), McGraw-Hill, Taiwan,57–64.
2. Johnson, N. L. and Kotz, S. (1977). Urn Models and Their Application: An Approach to Modern Discrete Probability Theory.Wiley, New York.
3. Johnson, N. L., Kotz, S. and Kemp, A. W. (1992).Univariate Discrete Distributions,Second Edition. Wiley, New York.
4. Johnson, N. L., Kotz, S. and Balakrishnan, N. (1995).Continuous Univariate Distributions,Vol. 2, Second Edition. Wiley, New York.
5. Mahmoud, H. M. (2008).Polya Urn Models.Chapman & Hall/CRC, Boca Raton, Florida.