1. Tu G, Gao Z, Hu R, et al. The Geochemistry and Ore-forming Mechanism of the Dispersed Elements (in Chinese). Beijing: Geological Publishing House, 2004, 368–395
2. Tang X, Huang W. Trace elements in Chinese coals (in Chinese). Beijing: The Commercial Press, 2004. 6–11, 136–141, 293–310
3. Finkleman R B. Trace and Minor Elements in Coal. In: Engel M H, Macko S A, eds. Organic Geochemistry. New York: Plenum Press, 1993. 595–607
4. Swaine D J. Trace Elements in Coal. London: Butterworths, 1990. 1–292
5. Bouška V, Pešek J. Quality parameters of lignite of the North Bohemian Basin in the Czech Republic in comparison with the world average lignite. International Journal of Coal Geology, 1999, 40: 211–235