Gan, D., Kotob, S. I. and Walia, D. S. (2007) “Evaluation of a Spectrophotometric Method for Practical and Cost Effective Quantification of Fulvic Acid”, Annals of Environmental Science, 1. Available at: https://openjournals.library.northeastern.edu/aes/journal/article/view/v1art2 (Accessed: 3 May 2024).