1. Barker J (1905) Letter to James Bertram, 7 June. Carnegie Corporation of New York Archives, Columbia University, New York.
2. Bertram J (1905a) Letter to John Barker, 20 June. Carnegie Corporation of New York Archives, Columbia University, New York.
3. Bertram J (1905b) Letter to JT Thompson, 12 September. Carnegie Corporation of New York Archives, Columbia University, New York.