Question: What was the middle name of the pianist who first performed Prokofiev's Piano Sonata No. 8?

full_context: Document 1: Piano Sonata No. 7 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 7 in B♭ major, Op. 83 (1942) (occasionally called the "Stalingrad") is a sonata composed for solo piano, the second of the three "War Sonatas". The sonata was first performed on 18 January 1943 in Moscow by Sviatoslav Richter.
Document 2: Piano Sonata No. 9 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 9 in C major, Op. 103 (1947) is a sonata for solo piano composed in 1947 and consists of four movements. The sonata was dedicated to Sviatoslav Richter, a member of the Union of Soviet Composers, and by whom it was first performed on 21 April 1951 in Moscow.
Document 3: Vladimir Horowitz discography: The Russian-American classical virtuoso pianist Vladimir Horowitz was a recording artist for over 60 years; beginning in 1926 on a piano roll system for Welte-Mignon, then with audio recordings, starting in 1928 for the Victor Talking Machine Company, later RCA Victor. Horowitz continued to record for a variety of record labels throughout his life. Between 1962 and 1973 he recorded for Columbia Masterworks In 1975, Horowitz returned to RCA, with which he recorded a series of live recitals. For the last years of his life, between 1985 and 1989, Horowitz recorded for Deutsche Grammophon. Horowitz’s final recording, with Sony Classical, was completed in November 1989, four days before his death. This final recording consisted of repertoire that he had never previously recorded.
Document 4: Glenn Gould: Glenn Herbert Gould ( ; 25 September 19324 October 1982) was a Canadian pianist who became one of the best-known and most celebrated classical pianists of the 20th century. He was particularly renowned as an interpreter of the keyboard music of Johann Sebastian Bach. His playing was distinguished by remarkable technical proficiency and capacity to articulate the polyphonic texture of Bach's music. He is widely considered one of the greatest pianists of the 20th century.
Document 5: Piano Sonata No. 3 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 3 in A minor, Op. 28 (1917) is a sonata composed for solo piano, using sketches dating from 1907. Prokofiev gave the première of this in St. Petersburg on April 15, 1918, during a week-long festival of his music sponsored by the Conservatory.
Document 6: Dmitri Shostakovich: Dmitri Dmitriyevich Shostakovich (Russian: Dmitriy Dmitrievich Shostakovich , ] ; 25 September [O.S. 12 September] 1906 9 August 1975) was a Russian composer and pianist. He is regarded as one of the major composers of the 20th century.
Document 7: Edna Golandsky: Edna Golandsky is a classical music pianist, lecturer and pedagogue of renown. She is a graduate of the Juilliard School, where she studied under Rosina Lhevinne and Adele Marcus. She later studied privately during many years with noted pedagogue Dorothy Taubman, whom she considers her main influence. She has earned wide acclaim throughout the United States and abroad for her extraordinary ability to solve technical problems at the instrument and for her penetrating musical insight. Many well-known concert pianists frequently play for her in her New York studio, including Chopin Competition laureate Gabriela Montero and Leeds Competition winner Ilya Itin. Golandsky co-founded the Taubman Institute, of which she was Associate Artistic Director from 1976-2002.
Document 8: Piano Sonata No. 4 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 4 in C minor, Op. 29 (1917) is a sonata composed for solo piano. It was first performed by the composer on April 17, 1918, in Petrograd. The work was dedicated to Prokoviev's good friend Maximilian Schmidthof, whose suicide in 1913 shocked and saddened the composer.
Document 9: Piano Sonata No. 6 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 6 in A major, Op. 82 (1940) is a sonata for solo piano, the first of the Three War Sonatas. The sonata was first performed on 8 April 1940 in Moscow.
Document 10: Heinrich Neuhaus: Heinrich Gustavovich Neuhaus (Russian: Ге́нрих Густа́вович Нейга́уз , "Genrikh Gustavovič Nejgauz"; 12 April [O.S. 31 March] 1888 10 October 1964) was a Soviet pianist and pedagogue of German extraction. He taught at the Moscow Conservatory from 1922 to 1964. He was made a People's Artist of the RSFSR in 1956. His pedagogic book "The Art of Piano Playing" (1958) is regarded as one of the most authoritative and most widely used treatments on the subject. He died in Moscow in 1964.
Document 11: Martha Argerich: Martha Argerich (born June 5, 1941) is an Argentine classical pianist, who is widely regarded as one of the greatest pianists of the second half of the 20th century.
Document 12: Piano Sonata No. 8 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 8 in B♭ major, Op. 84 (1944) is a sonata for solo piano, the third of the Three War Sonatas. The sonata was first performed on 30 December 1944 in Moscow by Emil Gilels.
Document 13: Emil Gilels: Emil Grigoryevich Gilels (sometimes transliterated "Hilels"; , Russian: Эми́ль Григо́рьевич Ги́лельс , "Emiľ Grigorievič Gileľs "; 19 October 1916 – 14 October 1985) was a Soviet pianist, widely regarded as one of the greatest pianists of the 20th century.
Document 14: Piano Sonata No. 5 (Prokofiev): Sergei Prokofiev's Piano Sonata no. 5 in C major, Op. 38 (1923) and Op. 135 (revised 1952-53) is a sonata for solo piano. Prokofiev composed the sonata in Ettal, by the Bavarian Alps, and dedicated it to Pierre Souvtchinski, a musicologist and friend. Even though the revised version of the sonata has a new opus number, if one compares the two versions closely, there are few radical differences between the two, with most of the changes occurring in the last movement. This sonata was the only piano piece of this genre to be composed during his life outside of Russia.
Document 15: Sviatoslav Richter: Sviatoslav Teofilovich Richter (Russian: Святосла́в Теофи́лович Ри́хтер , "Sviatosláv Teofílovich Ríkhter"; ] ; March 20 [O.S. March 7] 1915 – August 1, 1997) was a Soviet pianist known for the depth of his interpretations, virtuoso technique, and vast repertoire. He is considered one of the greatest pianists of the 20th century.
ground_truth: Grigoryevich