Christopher Innes (a cura di), The Cambridge Companion to George Bernard Shaw, Cambridge . Cambridge University press, 1998, p. 26, ISBN 1139825569, ISBN 9781139825566 (Google libri)
Leonard W. Conolly, Bernard Shaw and the BBC, Toronto etc.: University of Toronto press, 2009, p. 79, ISBN 9780802089205 (Google libri)