BOGOLYUBOV (JUNIOUR), N. N.; PRIKARPATSKY , A. K. Bilocal periodic problem for the Sturm-Liouville and Dirak operators as well as certain applications in the theory of nonlinear dynamic systems. I . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 42, n. 6, p. 794–800, 1990. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8839. Acesso em: 6 dec. 2025.