Pupalaigė, K., M. Sapagovas, and R. Čiupaila. “Nonlinear Elliptic Equation With Nonlocal Integral Boundary Condition Depending on Two Parameters”. Mathematical Modelling and Analysis, vol. 27, no. 4, Nov. 2022, pp. 610–628, doi:10.3846/mma.2022.16209.