Andrew Gann, 'Theophile Gautier, Charles Gounod, and the massacre of La Nonne sanglante,' Journal of Musicological Research 13, no. 1–2 (1993), 49–66. See also Anne Williams article re La Nonne sanglante: Stephen Huebner, The Operas of Charles Gounod (Clarendon Press, Oxford 1990).