Hummel, H. (1988). Introduction to the Schelde symposium, in: Hummel, H. et al. (Ed.) Hydrobiology and chemistry of the Schelde and Westerschelde: proceedings of the Schelde symposium (May 1987, Terneuzen, The Netherlands). pp. I-VI
In: Hummel, H. et al. (Ed.) (1988). Hydrobiology and chemistry of the Schelde and Westerschelde: proceedings of the Schelde symposium (May 1987, Terneuzen, The Netherlands). Delta Institute for Hydrobiological Research: Yerseke. VI, 67 pp., meer