APA

Verma P. S. A. V. K., . (1983). Principles of ecology. : S Chand & Co. Pvt. Ltd., New Delhi.

Chicago

Verma P S Agarwal V K, . 1983. Principles of ecology. : S Chand & Co. Pvt. Ltd., New Delhi.

Harvard

Verma P. S. A. V. K., . (1983). Principles of ecology. : S Chand & Co. Pvt. Ltd., New Delhi.

MLA

Verma P S Agarwal V K, . Principles of ecology. : S Chand & Co. Pvt. Ltd., New Delhi. 1983.