Dickens, Charles (1883). Dickens's Dictionary of Paris, p. 221. London: Macmillan. Full view at Google Books.
Fontaine 2003, p. 23, says Duponchel and Pillet became co-directors on 1 June 1841 (without Monnais). On this date Monnais was appointed to a position as Royal Commissioner (Walton 1898, p. 294). Fontaine, perhaps in error, omits the 1 June 1840 co-directorship of Duponchel, Monnais, and Pillet.
doi.org
"Book Reviews: Napoléon et l'Opéra: La politique sur la scéne, 1810–1815 by David Chaillou." The English Historical Review122 (496): 486–490 (2007). doi:10.1093/ehr/cem021.