Adekunle, Iheoma M, Toyin A Arowolo, Naomi P Ndahi, Babajide Bello, and David A. Owolabi. “Chemical Characteristics of Humic Acids in Relation to Lead, Copper and Cadmium Levels in Contaminated Soils from South West Nigeria”. Annals of Environmental Science 1 (March 7, 2007). Accessed August 5, 2026. https://openjournals.neu.edu/aes/journal/article/view/v1art4.