A note of existence of $T$-periodic solutions of the nonlinear scalar differential equations with maxima. Neliniini Kolyvannya, [S. l.], v. 1, n. 1, p. 1–5, 1998. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/3. Acesso em: 22 jan. 2026.