Hellawell, J. M. 1977.
Hellawell, J. M. 1977. Change in Natural and Managed Ecosystems: Detection, Measurements and Assessment. Proc. Royal Soc. London. B. 197:31-57
Hellawell, J. M. 1977. Change in Natural and Managed Ecosystems: Detection, Measurements and Assessment. Proc. Royal Soc. London. B. 197:31-57