1. [1] Cohn, R. M., Difference Algebra, Interscience Publishers John Wiley & Sons, New York-London-Sydney, 1965.
2. [2] Gasper, G. and Rahman, M., Basic Hypergeometric Series, Second edition, Encyclopedia of Mathematics and Its Applications, 96, Cambridge University Press, Cambridge, 2004.
3. [3] Grammaticos, B. and Ramani, A., Discrete Painlevé equations: a review, Lecture Note in Phys., 644, Springer, Berlin, 2004, pp. 245-321.
4. [4] Kajiwara, K., Nakazono, N. and Tsuda, T., Projective reduction of the discrete Painlevé system of type (A2 + A1)(1), Int. Math. Res. Not. IMRN, 2011 (2011), 930-966.
5. [5] Koekoek, R., Lesky, P. A. and Swarttouw, R. F., Hypergeometric orthogonal polynomials and their q-analogues, Springer Monographs in Mathematics, Springer-Verlag, Berlin, 2010.