1. Quotients of Primes
2. T. A. Apostol, Mathematical Analysis, second edition, Addison-Wesley, Reading, 1977.
3. G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, fifth edition, Clarendon Press, Oxford, 1979.
4. P. Ribenboim, The Book of Prime Number Records, second edition, Springer-Verlag, New York, 1989.