13. Wijaya, N. & Zhang, L. (2011) A critical review of coal demineralization and its implication on understanding the speciation of organically bound metals and submicrometer mineral grains in coal. Energy Fuel 25(1), 1. DOI: 10.1021/ef100819210.1021/ef1008192.10.1021/ef100819210.1021/ef1008192
14. Ning, X. & Xiuxiang, T. (2015) Changes in sulfur form during coal desulfurization with microwave: Effect on coal properties. International J. 3, 016.