APA
Dury G. H., . (1981). An introduction to environmental systems. London: Heinemann.
Chicago
Dury George H, . 1981. An introduction to environmental systems. London: Heinemann.
Harvard
Dury G. H., . (1981). An introduction to environmental systems. London: Heinemann.
MLA
Dury George H, . An introduction to environmental systems. London: Heinemann. 1981.