Novickij, Jurij, and Artūras Štikonas. “On the Stability of a Weighted Finite Difference Scheme for Wave Equation With Nonlocal Boundary Conditions”. Nonlinear Analysis: Modelling and Control, vol. 19, no. 3, Oct. 2014, pp. 460-75, https://doi.org/10.15388/NA.2014.3.10.