Stefanova, M., and S.P. Marinov. “ORGANIC GEOCHEMISTRY OF HUMIC ACIDS FROM A NEOGENE LIGNITE SAMPLE, BULGARIA”. Bulletin of the Geological Society of Greece 43, no. 5 (January 1, 2010): 2398–2405. Accessed November 22, 2024. https://ejournals.epublishing.ekt.gr/index.php/geosociety/article/view/11640.