1. U.S. Public Law 101-549. Clean Air Act Amendments, Title 3. 104 Stat 2531–2535, 1990.
2. Trace elements in coal;Swaine,1990
3. Trace elements — emission from coal combustion and gasification;Clarke,1992
4. Wesnor JD. ABB's investigation into the utility air toxic problems. Paper presented at EPRI/EPA SO2 Conference, Boston, MA, 1993.
5. Trace elements in coal;Davidson,1996