Horodnii , M. F., and V. P. Kravets. “Bounded Solutions of a Second-Order Difference Equation With Jumps of Operator Coefficients”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 73, no. 3, Mar. 2021, pp. 335 -40, doi:10.37863/umzh.v73i3.6058.