The Marriage of Figaro (English Wikipedia)

Broder, Nathan (1951). "Essay on the Story of the Opera". The Marriage of Figaro: Le Nozze di Figaro. By Mozart, Wolfgang Amadeus; Da Ponte, Lorenzo (piano reduction vocal score). Translated by Martin, Ruth; Martin, Thomas. New York: Schirmer. pp. v–vi. (Quoting Memoirs of Lorenzo da Ponte, transl. and ed. by L. A. Sheppard, London: Routledge & Kegan Paul, 1929, pp. 129ff
The letter, to Marianne von Genzinger, is printed in Geiringer & Geiringer 1982, pp. 90–92 Geiringer, Karl; Geiringer, Irene (1982). Haydn: A Creative Life in Music (3rd ed.). University of California Press. pp. xii, 403. ISBN 0-520-04316-2.
Landon & Jones 1988, p. 174 Landon, H. C. Robbins; Jones, David Wyn (1988). Haydn: His Life and Music. Indiana University Press. ISBN 978-0-253-37265-9.
See Robinson 1986, p. 173; Chanan 1999, p. 63; and Singher & Singher 2003, p. 150. Mozart (and his contemporaries) never used the terms "mezzo-soprano" or "baritone" (although the NMA score lists Almaviva as baritono. Women's roles were listed as either "soprano" or "contralto", while men's roles were listed as either "tenor" or "bass". Many of Mozart's baritone and bass-baritone roles derive from the basso buffo tradition, where no clear distinction was drawn between bass and baritone, a practice that continued well into the 19th century. Similarly, mezzo-soprano as a distinct voice type was a 19th-century development (Jander et al. 2001, chapters "Baritone" and "Mezzo-soprano [mezzo]"). Modern re-classifications of the voice types for Mozartian roles have been based on analysis of contemporary descriptions of the singers who created those roles and their other repertoire, and on the role's tessitura in the score. Robinson, Paul A. (1986). Opera & Ideas: From Mozart to Strauss. Cornell University Press. p. 173. ISBN 0-8014-9428-1. Chanan, Michael (1999). From Handel to Hendrix: The Composer in the Public Sphere. Verso. ISBN 1-85984-706-4. Singher, Martial; Singher, Eta (2003). An Interpretive Guide to Operatic Arias: A Handbook for Singers, Coaches, Teachers, and Students. Penn State University Press. ISBN 0-271-02354-6. Jander, Owen; Steane, J. B.; Forbes, Elizabeth; Harris, Ellen T.; Waldman, Gerald (2001). Stanley Sadie; John Tyrrell (eds.). The New Grove Dictionary of Music and Musicians (2nd ed.). Macmillan. ISBN 0-333-60800-3.
Thomas, Hugh (2006). "Ten – Leaving Madrid.". Beaumarchais in Seville: an intermezzo. New Haven: Yale University Press. p. 143. ISBN 978-0-300-12103-2. Retrieved 27 August 2008. Synopsis based on Melitz 1921, pp. 251–254.
Rosen 1997, p. 182. Rosen, Charles (1997). The Classical Style: Haydn, Mozart, Beethoven (2nd ed.). New York: W. W. Norton. ISBN 0-393-31712-9. (At archive.org)
Rosen 1997, p. 183. Rosen, Charles (1997). The Classical Style: Haydn, Mozart, Beethoven (2nd ed.). New York: W. W. Norton. ISBN 0-393-31712-9. (At archive.org)
Bishop, Henry R. (1819). The Marriage of Figaro: A Comic Opera in Three Acts. Piccadilly: John Miller.

bachtrack.com

"Belly laugh: Verdi's Falstaff ends CBSO season in high spirits" by Mark Pullinger, Bachtrack, 14 July 2016

books.google.com

While the political content was suppressed, the opera enhanced the emotional content. According to Stendhal, Mozart "transformed into real passions the superficial attachments that amuse Beaumarchais's easy-going inhabitants of [Count Almaviva's castle] Aguas Frescas". Stendhal's French text is in: Dümchen, Sybil; Nerlich, Michael, eds. (1994). Stendhal – Text und Bild (in German). Tübingen: Gunter Narr. ISBN 978-3-8233-3990-8.
See Robinson 1986, p. 173; Chanan 1999, p. 63; and Singher & Singher 2003, p. 150. Mozart (and his contemporaries) never used the terms "mezzo-soprano" or "baritone" (although the NMA score lists Almaviva as baritono. Women's roles were listed as either "soprano" or "contralto", while men's roles were listed as either "tenor" or "bass". Many of Mozart's baritone and bass-baritone roles derive from the basso buffo tradition, where no clear distinction was drawn between bass and baritone, a practice that continued well into the 19th century. Similarly, mezzo-soprano as a distinct voice type was a 19th-century development (Jander et al. 2001, chapters "Baritone" and "Mezzo-soprano [mezzo]"). Modern re-classifications of the voice types for Mozartian roles have been based on analysis of contemporary descriptions of the singers who created those roles and their other repertoire, and on the role's tessitura in the score. Robinson, Paul A. (1986). Opera & Ideas: From Mozart to Strauss. Cornell University Press. p. 173. ISBN 0-8014-9428-1. Chanan, Michael (1999). From Handel to Hendrix: The Composer in the Public Sphere. Verso. ISBN 1-85984-706-4. Singher, Martial; Singher, Eta (2003). An Interpretive Guide to Operatic Arias: A Handbook for Singers, Coaches, Teachers, and Students. Penn State University Press. ISBN 0-271-02354-6. Jander, Owen; Steane, J. B.; Forbes, Elizabeth; Harris, Ellen T.; Waldman, Gerald (2001). Stanley Sadie; John Tyrrell (eds.). The New Grove Dictionary of Music and Musicians (2nd ed.). Macmillan. ISBN 0-333-60800-3.
Angermüller, Rudolph (1 November 1988). Mozart's Operas. Rizzoli. p. 137. ISBN 9780847809936.
Brown-Montesano, Kristi (2007). Understanding the Women of Mozart's Operas, p. 207. University of California Press. ISBN 052093296X
Gossett, Philip (2008). Divas and Scholars: Performing Italian Opera, pp. 239–240. University of Chicago Press. ISBN 0226304876
Cairns, David (2007). Mozart and His Operas. Penguin. p. 256. ISBN 9780141904054. Retrieved 19 August 2014.