Dawson, W. R. (1946). “On the History of Gray and Hardwicke’s Illustrations of Indian Zoology, and Some Biographical Notes on General Hardwicke”, Journal of the Society for the Bibliography of Natural History2 (3), p. 55–69. doi:10.3366/jsbnh.1946.2.3.55.
Kinnear, NB (1925). “The Dates of Publication of the Plates of the Birds in Gray and Hardwicke's ‘Illustrations of Indian Zoology’ with a short Account of General Hardwicke”, Ibis67 (2), p. 484–489. doi:10.1111/j.1474-919X.1925.tb02936.x.