1. For a discussion on the passport controversy see J. P. O’Grady, ‘The Irish Free State Passport and the Question of Citizenship 1921–24’, Irish Historical Studies, vol. 26, no. 104 (November 1989)
2. G. MacMillan, ‘British Subjects and Irish Citizens: The Passport Controversy 1923–24’, Eire-Ireland, vol. 26, no. 3 (1991)
3. D. W. Harkness, The Restless Dominion: The Irish Free State and the British Commonwealth of Nations (London, 1969), p. 47.
4. G. Martin, ‘The Irish Free State and the Evolution of the Commonwealth 1921–1949’, in R. Hyam and G. Martin (eds.), Reappraisals in British Imperial History (London, 1975).
5. N. McQueen, ‘Eamon de Valera, the Irish Free State and the League of Nations 1919–46’, Eire-Ireland, vol. 17, no. 4 (1982).