6Dalway J Swaine. Why Trace Elements are Important [ J ]. Fu-el Processing Technology, 2000 (65/66): 21-23.
7Robert B Finkelmana. Modes of Occurrence of Potentially Haz- ardous Elements in Coal: Levels of Confidence [ J ]. Fuel Pro- eessing Technology, 1994, 39: 21-34.
8Maria Mastalerz, Agnieszka Drobniak. Aenic, Cadmium, Lead and Zinc in the Danville and Springfield Coal Members ( Pennsylvanian ) from Indiana [ J ]. International Journal of Coal Geology, 2007, 71: 37-53.
9Gerald H Luttrell, Jaisen N Kohmuench. An Evaluation of Coal Preparation Technologies for Controlling Trace Element Emis- sions [ J ]. Fuel Processing Technology, 2000, 66 (6) : 407-422.