GEEM, Methaq Hamza. On optimal periodic solution of differential equations. Journal of Kufa for Mathematics and Computer, Kufa, Najaf, IRAQ, v. 5, n. 1, p. 21–24, 2018. DOI: 10.31642/JoKMC/2018/050103. Disponível em: https://journal.uokufa.edu.iq/index.php/jkmc/article/view/2095. Acesso em: 24 apr. 2026.