1. I.G. Malkin, Some problems of the theory of nonlinear oscillations. M., Gostekhizdat, 1956 (in Russian).
2. A.A. Boichuk and A.M. Samoilenko, Generalized inverse operators and Fredholm boundary-value problems; 2nd edition. Berlin; Boston, De Gruyter, 2016.
3. S. Chuiko and O. Nesmelova, A periodic problem for a Rayleigh-type equation unsolved with respect to the derivative. Ukrainian Mathematical Journal, 75(10), 1429–1440 (2023).
4. O. Vejvoda, On perturbed nonlinear boundary-value problems. Czech. Math. J., 11, 323–364 (1961).
5. A. Boichuk and S. Chuiko, “Autonomous Weakly Nonlinear Boundary Value Problems in Critical Cases,” Differential Equations, 10, 1353–1358 (1992).