A. M. Samoilenko, . S. M. Chuiko, and . O. V. Nesmelova, “Nonlinear boundary-value problems unsolved with respect to the derivative”, Ukr. Mat. Zhurn., vol. 72, no. 8, pp. 1106–1118, Aug. 2020, doi: 10.37863/umzh.v72i8.5986.