Udo, E. J., N. P. Uto, A. E. Anieting, V. O. Ezugwu, and E. J. Inyang. “The Contribution of Some Revenue Sources to the Total Expenditure of an Oil-Producing State in Nigeria”. World Journal of Applied Science & Technology, vol. 18, no. 1, Aug. 2026, pp. 79-83, https://www.ajol.info/index.php/wojast/article/view/334339.