1. Arnold, G. W., 1964. Factors within plant associations affecting the behaviour and performance of grazing animals. In: D. J. Crisp (ed.). Grazing in Terrestrial and Marine Environments, pp. 133?154. Blackwell, Oxford.
2. Bakker, J. P. & Ruyter, J. C., 1981. Effects of five years of grazing on a salt-marsh vegetation-a study with sequential mapping. Vegetatio 44: 81?100.
3. Bakker, J. P. & Bie, S.de, Dallinga, J. H., Tjaden, P. & Vries, Y.de, 1983. Sheep grazing as a management tool for heathland conservation and regeneration in the Netherlands. J. Appl. Ecol. 20: 541?560.
4. Bakker, P. A., 1979. Vegetation science and nature conservation. In: M. J. A. Werger (ed.). The Study of Vegetation, pp. 247?288. Junk, The Hague.
5. Black, J. S., 1957. The digestibility of indigenous hill pasture species. Rep. Hill Farming Res. Org. 4: 33?37.