1. Water in the Netherlands: a Time for Action, National Policy Document on Water Management, House of Comments, Meeting period 1988/1989, The Hague, no. 21250 (1–2).
2. D. Froehlich, W. Meier, J. High Resolut. Chromatogr.,12, 340 (1989).
3. E. Zietz, I. Ricker, J. Planar Chromatogr.,2, 262 (1989).
4. M. Grandet, L. Weil, K.-E. Quentin, Z. Wasser-Abwasser Forsch.,21, 21 (1988).
5. G. A. Junk, J. J. Richard, Anal. Chem.,60, 451 (1988).