W. E. L. G. Clark. The fossil evidence for human evolution. University of Chicago Press, 1964. W. E. L. G. Clark, Clark, and B. G. Campbell. The Fossil Evidence for Human Evolution: An Introduction to the Study of Paleoanthropology. University of Chicago Press, 1955. M. A. C. Hinton, K. P. Oakley, H. G. Dines, W. B. R. King, A. S. Kennard, C. F. C. Hawkes, S. H. Warren, M. A. Cotton, W. E. L. G. Clark, and G. M. Morant. Report on the Swanscombe Skull. The Journal of the Royal Anthropological Institute of Great Britain and Ireland, JSTOR, volume 68, pages 17, January 1938.