1. W. G. Kelley and A. C. Peterson, Difference Equations: An Introduction with Applications, Academic Press, New York, 1991.
2. C. Gao, L. Lv, and Y. Wang, Spectra of a discrete Sturm-Liouville problem with eigenparameter-dependent boundary conditions in Pontryagin space, Quaest. Math. (2019), 1–26, 10.2989/16073606.2019.1680456.
3. D. Aharonov, M. Bohner, and U. Elias, Discrete Sturm comparison theorems on finite and infinite intervals, J. Differ. Equ. Appl. 18 (2012), no. 10, 1763–1771, 10.1080/10236198.2011.594440.
4. R. P. Agarwal and D. O’Regan, Boundary value problems for discrete equations, Appl. Math. Lett. 10 (1997), no. 4, 83–89, 10.1016/S0893-9659(97)00064-5.
5. R. P. Agarwal and F.-H. Wong, Existence of positive solutions for nonpositive difference equations, Math. Comput. Model. 26 (1997), no. 7, 77–85, 10.1016/S0895-7177(97)00186-6.