"Incredible Quotations: 230 Thought-Provoking Quotes with Prompts to Spark Students' Writing, Thinking, and Discussion". Book by Jacqueline Sweeney, 1997.
Ludwig van Beethoven, Friedrich Kerst, Henry Edward Krehbiel (1964). “Beethoven, the Man and the Artist, as Revealed in His Own Words”, p.13, Courier Corporation
Attributed to Ludwig van Beethoven by Bettina von Arnim in a letter to Goethe (May 28, 1810), as quoted in Bettina von Arnim "Goethe's Correspondence with a Child", 1835.