Earlier incarnations of the Doctor have at times appeared with the then latest incarnation in later plots. Notably, in 2013, John Hurt guest-starred as a hitherto unknown incarnation of the Doctor acknowledged as the War Doctor in the operate-up to the show's 50th-anniversary unique "The Day of the Doctor". Saxe, John Godfrey (1872). "The Blindmen and the Elephant" at Wikisource. The Poems of John Godfrey Saxe. Moss, C. "Elephant Calves: The Story of Two Sexes". Payne, K. B. Langauer, W. B. "Elephant Communication". Larom, D. Garstang, M. Payne, K. Raspet, R. Lindeque, M. (1997). "The influence of floor atmospheric circumstances on the selection and location arrived at by animal vocalizations" (PDF). Herbest, C. T. Stoeger, A. Frey, R. Lohscheller, J. Titze, I. R. Gumpenberger, M. Fitch, W. T. (2012). "How Low Can You Go? Physical Production Mechanism of Elephant Infrasonic Vocalizations". O'Connell-Rodwell, C. E. Wood, J. D. Rodwell, T. C. Puria, S. Partan, S. R. Keefe, R. Shriver, D. Arnason, B. T. Hart, L. A. (2006). "Wild elephant (Loxodonta africana) breeding herds respond to artificially transmitted seismic stimuli" (PDF). Slotow, R. van Dyk, G. Poole, J. Page, B. Klocke, A. (2000). "Older bull elephants management young males". Douglas-Hamilton, I. Bhallaa, S. Wittemyera, G. Vollratha, F. (2006). "Behavioural reactions of elephants towards a dying and deceased matriarch" (PDF)
McComb, K. Baker, L. Moss, C. (2006). "African elephants display large stages of desire in the skulls and ivory of their have species". Thouless, C.R. Dublin, H.T. Blanc, J.J. Skinner, D.P. Daniel, T.E. Taylor, R.D. Maisels, F. Frederick, H. L. Bouch