"Signs in Rotation" (1967) in "The Bow and the Lyre : The Poem, The Poetic Revelation, Poetry and History" by Octavio Paz, translated by Ruth L. C. Simms, (p. 249), 1973.
Ludwig van Beethoven (1868). “Letters from the Collection of Ludwig Nohl: Also His Letters to the Archduke Rudolph, Cardinal-Archbishop of Olmütz, K.W. from the Collection of Ludwig, Ritter Von Köchel. Translated by Lady Wallace, with a Portrait and Facsimile”, p.88