1. See (Krauss 2004: 107).
2. Quoted from (Reid 1976: 263).
3. Letter from Max Dehn to Erich Kamke, 13 August 1948, in: Max Dehn Papers, box 2, no. 55, (Austin, Archives of American Mathematics).
4. (Kamke 1951: 1).
5. Letter from Abraham Fraenkel to Erich Kamke, 29 January 1951 (Universitätsarchiv Tübingen).