1. Rabinowitz, P.H.: Minimax Methods in Critical Point Theory with Applications to Differential Equations. American Mathematical Society, Providence (1986)
2. Liu, X., Zhou, T., Shi, H.P., Long, Y.H., Wen, Z.L.: Periodic solutions with minimal period for fourth-order nonlinear difference equations. Discrete Dyn. Nat. Soc. 2018, Article ID 4376156 (2018)
3. Ma, R.Y., Lu, Y.Q.: Existence and multiplicity of positive solutions of a nonlinear discrete fourth-order boundary value problem. Abstr. Appl. Anal. 2012, Article ID 918082 (2012)
4. Onozaki, T., Sieg, G., Yokoo, M.: Complex dynamics in a cobweb model with adaptive production adjustment. J. Econ. Behav. Organ. 41(2), 101–115 (2000)
5. Goldberg, S.: Introduction to Difference Equations: With Illustrative Examples from Economics, Psychology, and Sociology. John Wiley, New York (1958)