1. Abbas, M.Z.M., Bruns, R.E., Scarminio, I.S., and Ferreira, J.R.: 1993,Environ. Pollut. 79, 225.
2. AOAC (Association of Official Analytical Chemists): 1975,J. of the AOAC 58, 384.
3. Arndt, U. and Schweizer, B.: 1991, ?The Use of Bioindicators for Environmental Monitoring in Tropical and Subtropical Countries', in Ellenberg, H. (ed.),Biological Monitoring ? Signals from the Environment, Vieweg, Braunschweig, Germany, pp. 199?260.
4. Arndt, U., Erhardt, W., Keitel, A., Michenfelder, K., Nobel, W., and Schlüter, C.: 1985,Staub ? Reinhalt. Luft 45, 481.
5. Carlson, C.E.: 1973,Fluoride,6, 127.