System of Non-Linear Volterra Integral Equations in a Direct-Sum of Hilbert Spaces. Journal of the Nigerian Society of Physical Sciences, [S. l.], v. 4, n. 4, p. 1021, 2022. DOI: 10.46481/jnsps.2022.1021. Disponível em: https://www.journal.nsps.org.ng/index.php/jnsps/article/view/1021.. Acesso em: 28 apr. 2024.