- British Library, The: BL Add. 46434 ff. 292-293
- Natural History Museum, London: NHM WP6/4/1
- Marchant, J. (Ed.). (1916). In: Alfred Russel Wallace; Letters and Reminiscences. Vol. 1. London & New York: Cassell & Co. [pp. 307-308]
- Wallace, A. R. (1908). In: My Life: a Record of Events and Opinions (2nd edition). London: Chapman & Hall. [p. 232]
No summary available.