References
- Claassen, T. H. L., De Graaf, C. Th. & Arts, G. H. P., 1992: Ecological management programmes for broads and peat ponds in Friesland, The Netherlands. — H2O 25, 222 — 227 & 232. (in Dutch, summary in English).
- Grontmij, 1991: Ecological management programmes for broads and peat ponds in Friesland; specific programme for De Deelen. — 47 pp. De Bilt. (in Dutch).
- Groot, K., 1991: Phosphate exchange by the sediment of some Frisian lakes. — 39 pp. RIZA, Lelystad, (in Dutch).
- Iwaco, 1990: Studies of the water balance and management alternatives for De Deelen. — 50 pp. Groningen. (in Dutch).
- Raat, A. J. P. & De Laak, G. A. J., 1990: The fish stock in De Deelen in March 1990. — 27 pp. OVB, Nieuwegein. (in Dutch).
- Smit, M. D. & De Jongh, A. W. J. J., 1991: PCB contamination of otter areas in The Netherlands. Proceedings V. Internat. Otter Colloquium Hankelsbüttel: 229–234.