1. National Nature Policy Plan,1990
2. Ecohydrology and fen plant distribution in the Vechtplassen area, The Netherlands;Beltman,1991
3. Management and restoration of the drainage system of floating fens;Beltman,1994
4. Restoration of acidified rich-fen ecosystems in the Vechtplassen area: Successes and failures;Beltman,1995