Joseph Lancaster (1807). “Improvements in Education, as it Respects the Industrious Classes of the Community: Containing Among Other Important Particulars, an Account of the Institution for the Education of One Thousand Poor Children, Borough Road, Southwark; and of the New System of Education on which it is Conducted”, p.154
Henry Moseley's letter to Margery Moseley (February 2, 1913), as quoted in "H. G. J. Moseley: The Life and Letters of an English Physicist 1887-1915" edited by J. L. Heilbron (p. 201), 1974.
"Does Some Deeper Level of Physics Underlie Quantum Mechanics? An Interview with Nobelist Gerard 't Hooft". Interview with George Musser, blogs.scientificamerican.com. October 7, 2013.