A history of western educational ideas / Denis Lawton and Peter Gordon. - Lawton, Denis. (OLS)http://pul/name/106758; Gordon, Peter. (OLS)http://pul/name/106759 (Woburn Press, 2002)
Bibliografia in nota.

Royce / Wim M. de Nier. - Nier, Vim M. de. (OLS)http://pul/name/42221; Pontificio Ateneo Salesiano Tesi. (OLS)http://pul/name/105057 (La Scuola, 1950)
Tesi. Pontificium Athenaeum Salesianum. Facultas Philosophica.1950.
Bibliografia in nota a piè pagina.