Contreras, Eliasara, Edgardo Leal, y Manuel Martínez. «Effect of Temperature, Oxidation Time and Substrate: Oxidant Agent Ratio in the Yield and Composition of Humic Acids Derived from Coal, Monitored by 1H NMR and FT-Ir». Rev. Téc. Fac. Ing. Univ. Zulia 27, no. 2 (noviembre 2, 2010). Accedido abril 10, 2025. https://mail.produccioncientificaluz.org/index.php/tecnica/article/view/5841.