Soares, J. D. R., R. A. L. S. Rezende, R. M. Rezende, E. P. Botrel, and A. M. de Carvalho. “Agricultural Waste Composting: A Source of Humic Substances”. Scientia Agraria Paranaensis, vol. 16, no. 4, Dec. 2017, pp. 414-21, https://e-revista.unioeste.br/index.php/scientiaagraria/article/view/16973.