1. Förstner, U., Wittmann, G.T.W.: Metal Pollution in the Aquatic Environment, 1981, Berlin, Springer-Verlag
2. Florence, T.M.: Talanta, 29, 345 (1982)
3. Golterman, H.L., Clymo, R.S., Ohnstad, M.A.M.: Methods for Physical and Chemical Analysis of Fresh Water, 1978, Oxford, Blackwell Scientific Publications
4. Fishman, M.J., Mallory, E.C.: J. Water Pollut. Control Fed., 40, R67 (1968)
5. Monien, H., Bovenkerk, R., Kringe, K.P., Rath, D.: Fresenius’ Z. Anal. Chem., 300, 363 (190)