1. Carlberg , G. 1975
2. Pennachetti , J. T. Boux , J. F. 1973
3. Murphy , E. M. Magnuson , M. O. Suder , P. , Jr Nagy , J. U.S. Bur. Mines Rep. Invest. 1968
4. Adams , L. M. Capp , J. P. Eisentrout , E. U.S. Bur. Mines Rep. Invest. 1971
5. Eldrige , E. Trans. 2nd Seminar Biological Problems on Water Pollution 1959 255