Niecks, Frederick (1890). FREDERICK CHOPIN AS A MAN AND MUSICIAN (Vol. II ed.). London & New York: Novello, Ewer & Co. p. 253. Retrieved 24 December 2015. life written another such beautiful melody.
Leichtentritt, Hugo. "Die Etüden". In Analyse der Chopin'schen Klavierwerke [Analysis of Chopin's Piano Works]. Band II. Berlin: Max Hesses Verlag, 1922, p. 95.