1. Champion HG, Seth SK (1968). Revised survey of forest types in India. The Manager of Publications, Delhi, Forest Research Institute, Dehradun, India.
2. Chaturvedi AN (1992). Environmental value of forest in Almora. In Agarwal, Anil. Ed. Prices of forests. New Delhi, Centre for Science and Environment.
3. Costanza R (1997). The value of the worlds ecosystem services and natural capital by. Nature 387(6630):253-260.
4. Daily GC (Ed.). (1997). Natures services. Societal dependence on natural ecosystems. Island Press, Washington, DC. 392 p. ISBN 1-55963-475-8 hbk), 1 55963 476 6 (soft cover).
5. Ehrlich PR, Ehrlich AH (1981). Extinction: the causes and consequences of the disappearance of species. Random House, New York. pp. 72-98.