^Gould, Frederick James. (1929). The Pioneers of Johnson's Court: A History of the Rationalist Press Association From 1899 Onwards. Watts. p. 54
^Anonymous. (1935). Obituary: Mr. Thomas Whittaker. Metaphysician and Critic. The Times. October 4. p. 16
^McCabe, Joseph. (1950). A Rationalist Encyclopaedia: A Book of Reference on Religion, Philosophy, Ethics, and Science. Watts. p. 334. "In England the philosophic writer T. Whittaker, and L. G. Rylands, supported Robertson in denying the historicity of Jesus."
^Hawton, Hector. (1971). Controversy: The Humanist/Christian Encounter. Pemberton Books. p. 173. ISBN978-0301710211