Adekunle, I. M. (2007) “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. Available at: https://openjournals.library.northeastern.edu/aes/journal/article/view/v1art4 (Accessed: 6 May 2024).