Huebner 1999, p. 477. Huebner, Steven (1999). French Opera at the Fin de Siècle: Wagnerism, Nationalism, and Style. Oxford: Oxford University Press. ISBN9780195189544. OCLC40043694.
Thielemann 2016, pp. 194–195. Thielemann, Christian (2016). My life with Wagner : fairies, rings, and redemption : exploring opera's most enigmatic composer. New York: Pegasus Books. pp. 194–195. ISBN978-1-68177-125-0. OCLC923794429.