Ghabbour, E. A., Davies, G., Daggett, J. L., Worgul, C. A., Wyant, G. A. and Sayedbagheri, M.-M. (2012) “Measuring the Humic Acids Content of Commercial Lignites and Agricultural Top Soils in the National Soil Project”, Annals of Environmental Science, 6. Available at: https://openjournals.neu.edu/aes/journal/article/view/v6art1 (Accessed: 22 September 2023).