1. Slater E. The creative personality. In: Roth M, Cowie V, eds. Psychiatry, Genetics and Pathography. A Tribute to Eliot Slater. London: Gaskell, 1979: 100–3.
2. Wegeler F, Ries F. Remembering Beethoven: The Biographical Notes of Franz Wegeler [1765–1848] and Ferdinand Ries [1748–1838]. Trans. Noonan F, Bauman F, Clark T. London: Deutsch, 1987:68. First published in German in 1838 and later edited by A Kalischer in 1906. Wegeler was a friend in Bonn until Beethoven departed for Vienna in 1792, and again in Vienna from 1794–6. Ries, composer and pianist, studied the piano with Beethoven in Vienna for four years and was devoted to him.