Životić Dragana, Bechtel A., Sachsenhofer R., Gratzer R., Radić D., Obradović M., Stojanović Ksenija. "Reprint of Petrological and organic geochemical properties of lignite from the Kolubara and Kostolac basins, Serbia: implication on grindability index" in International Journal of Coal Geology 157, Amsterdam, Netherlands:Elsevier BV (2015): 165-183. https://doi.org/10.1016/j.coal.2014.07.004 M21