1. Booth, G.: 1977, Rev. Prog. Colouration 8, 1.
2. Anliker, R.: 1977, Rev. Prog. Colouration 8, 60.
3. Porter, J.: 1973, J. Pollut. Engng. 27, 30.
4. Davies, R. A., Kaempf, H. J., and Clemens, M. M.: 1973, Chem. Ind. 827.
5. Morris, J. C. and Weber, W. J. Jr.: 1963, J. Am. Soc. Civ. Eng., San. Eng. Div. 89, SA6, 53.