Abdul, Raheem A, and I.B, M.O Obioh. “MONITORING NOX AND O3 IN URBAN ATMOSPHERE: A COLORIMETRIC APPROACH IN ILORIN, NIGERIA”. SADI International Journal of Science, Engineering and Technology (SIJSET), vol. 9, no. 3, Aug. 2022, pp. 14-30, https://sadijournals.org/index.php/SIJSET/article/view/221.