SHARMA, J. P. Liapunov Function of Certain Non Linear Differential Equations of the Third and Fourth Order. Defence Science Journal, [S. l.], v. 19, n. 4, p. 253–260, 2014. DOI: 10.14429/dsj.19.7498. Disponível em: https://publications.drdo.gov.in/ojs/index.php/dsj/article/view/7498. Acesso em: 18 aug. 2025.