Question: Sadko has written and Cardillac by Hindemith is an example of operas written in which style?

Context paragraphs:
Maria de Francesca-Cavazza: Maria de Francesca-Cavazza is a German operatic soprano and voice teacher.  Raised in the United States, she is a graduate of the Sherwood Conservatory of Music at the Columbia College Chicago where she was a pupil of Maria Hussa-Greve and Garvin Williamson.  In 1961, she won the Metropolitan Opera National Council Auditions.  Shortly thereafter, she moved to Germany to pursue further studies at the Hochschule für Musik Köln with Margarete Düren.  She made her professional opera debut in 1962 at the Cologne Opera in a minor role, and the following year performed her first leading role with that company as Tsaritsa Militrisa in Nikolai Rimsky-Korsakov's "The Tale of Tsar Saltan".  She then appeared as a leading soprano at several German opera houses, working as a member of the Opernhaus Wuppertal (1964-1965), the Kiel Opera House (1965-1967), the Staatsoper Nürnberg (1967-1976), and the Staatsoper Stuttgart (1976-1986).  As a guest artist, she has made appearances at the Bavarian State Opera, the Bayreuth Festival and the Vienna State Opera, among others.  She can be heard and seen in the role of the Cardillac's daughter in Hindemith's opera Cardillac, conducted by Wolfgang Sawallisch, on a 1985 Munich DVD issued by Deutsche Grammophon.  De Francesca-Cavazza has taught on the music faculties of conservatories in Munich and Nuremberg.

Mörder, Hoffnung der Frauen: Mörder, Hoffnung der Frauen ("Murderer, Hope of Women") is an opera in one act by Paul Hindemith, written in 1919 on a German libretto by Oskar Kokoschka which he based on his play of 1907.  The opera was the first in a triptych of expressionist one-act operas, the others being "Das Nusch-Nuschi", and "Sancta Susanna".  They were the first operas written by Hindemith.  The first two were premiered together in Stuttgart on 4 June 1921, all three were performed at the Frankfurt Opera in 1922.

Chamber opera: Chamber opera is a designation for operas written to be performed with a chamber ensemble rather than a full orchestra.  Early 20th century operas of this type include Paul Hindemith's "Cardillac" (1926).  Earlier small-scale operas such as Pergolesi's "La serva padrona" (1733) are sometimes known as chamber operas.

Russian opera: Russian opera (Russian: Ру́сская о́пера) is the art of opera in Russia.  Operas by composers of Russian origin, written or staged outside of Russia, also belong to this category, as well as the operas of foreign composers written or intended for the Russian scene.  These are not only Russian-language operas.  There are examples of Russian operas written in French, English, Italian, Latin, Ancient Greek, Japanese, or the multitude of languages of the nationalities that were part of the Empire and the Soviet Union.

Cardillac: Cardillac is an opera by Paul Hindemith in three acts and four scenes.  wrote the libretto based on characters from the short story "Das Fräulein von Scuderi" by E.T.A. Hoffmann.

Der Zar lässt sich photographieren: Der Zar lässt sich photographieren ("The Tsar Has his Photograph Taken"') is an opera buffa in one act by Kurt Weill, op. 21.  The German libretto was written by Georg Kaiser, and Weill composed the music in 1927.  It is a Zeitoper, a genre of music theatre which used contemporary settings and characters, satiric plots which often include technology and machinery.  Musically the Zeitoper genre tends to be eclectic and borrow from Jazz.  The genre has practically disappeared from the world's opera houses.  Historically the Zeitoper came to an abrupt end with the Nazi period, and after the war the cultureal institutions were perhaps hesitant to return to the lighter, often decadent and comic operas written before the holocaust changed the artistic perspective.  This conjecture is supported by the statistical fact that of all of Weill's, Schönberg's, Hindemith's and Krenek's works - it is these very shorter, satirical Zeitoper works that are no longer performed.

List of operas by Hindemith: This is a list of the operas written by the German composer Paul Hindemith (1895–1963).

Ruddigore: Ruddigore; or, The Witch's Curse, originally called Ruddygore, is a comic opera in two acts, with music by Arthur Sullivan and libretto by W. S. Gilbert.  It is one of the Savoy Operas and the tenth of fourteen comic operas written together by Gilbert and Sullivan.  It was first performed by the D'Oyly Carte Opera Company at the Savoy Theatre in London on 22 January 1887.

Sadko (opera): Sadko (Russian: Садко , the name of the main character) is an opera in seven scenes by Nikolai Rimsky-Korsakov.  The libretto was written by the composer, with assistance from Vladimir Belsky, Vladimir Stasov, and others.  Rimsky-Korsakov was first inspired by the Bylina of Sadko in 1867, when he completed a tone poem on the subject, his Op. 5.  After finishing his second revision of this work in 1891, he decided to turn it into a dramatic work.

Bodo Igesz: Bodo Igesz (February 7, 1935, Amsterdam - December 25, 2014, Manhattan) was a Dutch stage director who had an active career staging operas around the world during the second half of the 20th century.  He was particularly known for his work with the Metropolitan Opera where he worked for 25 years on the staging staff.  He also staged operas for the Salzburg Festival, and staged numerous operas for the Santa Fe Opera; including the United States premieres of Hindemith's "Cardillac" (1967), Schoenberg's "Die Jakobsleiter" (1968), Henze's "The Bassarids" (1968) and Aribert Reimann's "Melusine" (1972).

Supporting paragraphs: Sadko (opera) Cardillac
Answer: libretto