1. Beintema, A. J.: 1975, ?Meadow Birds in a Changed Land?, Natuur en Landschap 29, 73?84 (in Dutch).
2. Beintema, A. J.: 1979, ?Should We Employ a Standard for Meadow Birds??, Natuur en Milieu 79/3, 18?21 (in Dutch).
3. RIN-report 81/19;A. J. Beintema,1981
4. Meelis, E. and Keurs, W. J. Ter: 1976, ?Mapping of the Environment: A Scientific Activity??, Natuur en Landschap 30, 85?98 (in Dutch).
5. Ministry of Culture, Recreation and Social Affairs: 1979, Natural and Cultural Values in the Rural Area, Staatsuitgeverij, 's-Gravenhage 33 pp. (in Dutch).