Grewal Bikram, Harvey Bill, & Pfister, O. (2002). A photographic guide to the birds of india: And the indian subcontinent, including pakistan, nepal, bhutan, bangladesh, sri lanka and the maldives. Princeton University Press.

Grewal Bikram, Harvey Bill, and Otto Pfister. A Photographic Guide to the Birds of India: And the Indian Subcontinent, Including Pakistan, Nepal, Bhutan, Bangladesh, Sri Lanka and the Maldives. Princeton: Princeton University Press, 2002.

Grewal Bikram, et al. A Photographic Guide to the Birds of India: And the Indian Subcontinent, Including Pakistan, Nepal, Bhutan, Bangladesh, Sri Lanka and the Maldives. Princeton University Press, 2002.