Question: Elizabeth Violet Polunin is most notably know for her work with a Russian ballet impresario born in which year ?

Context paragraphs:
Sergei Diaghilev: Sergei Pavlovich Diaghilev ( ; Russian: Серге́й Па́влович Дя́гилев , "Sergei Pavlovich Dyagilev"; ] ; 31 March [O.S. 19 March] 1872 19 August 1929), usually referred to outside Russia as Serge, was a Russian art critic, patron, ballet impresario and founder of the Ballets Russes, from which many famous dancers and choreographers would arise.

Max Rabinoff: Max A. Rabinoff (March 9, 1877 – April 19, 1966) was a Russian-born, naturalized American opera and ballet impresario and international economic adviser.  By the time he had become a naturalized U.S. citizen in 1898 he had already started an international import-export company focusing on encouraging American-Russian commerce.  By 1908 he had entered the world of performing arts promotion, helping to organize the Chicago Philharmonic Orchestra and the Chicago Opera Company.  He is best known for founding the Boston Grand Opera Company in 1914, where he introduced American audiences to Russian ballerina Anna Pavlova and her Russian Ballet Company during his time as managing director from 1914-1917.  He also discovered, and soon married, singer Marie La Salle, who died less than two years after their marriage.

Sergey Dyagilev (ship): The Sergey Dyagilev (Russian: Сергей Дягилев ) is a "Dmitriy Furmanov"-class (project 302, BiFa129M) Soviet/Russian river cruise ship, cruising in the Volga – Neva basin.  The ship was built by VEB Elbewerften Boizenburg/Roßlau at their shipyard in Boizenburg, East Germany, and entered service in 1983.  The ship is named after Russian art critic, patron, ballet impresario and founder of the Ballets Russes Sergei Diaghilev.

Agrippina Vaganova: Agrippina Yakovlevna Vaganova (Russian: Агриппина Яковлевна Ваганова ; 26 June 1879 – 5 November 1951) was a Russian ballet teacher who developed the Vaganova method – the technique which derived from the teaching methods of the old "Imperial Ballet School" (today the "Vaganova Academy of Russian Ballet") under the "Premier Maître de Ballet" Marius Petipa throughout the mid to late 19th century, though mostly throughout the 1880s and 1890s.  It was Vaganova who perfected and cultivated this form of teaching the art of classical ballet into a workable syllabus.  Her "Fundamentals of the Classical Dance" (1934) remains a standard textbook for the instruction of ballet technique.  Her technique is one of the most popular techniques today.

Elizabeth Polunin: Elizabeth Violet Polunin, (née Hart), (21 May 1887- 1950) was a British artist and theatre designer, most notably for her work with Sergei Diaghilev and the Ballets Russes.

Sergei Polunin: Sergei Vladimirovich Polunin (, "Serhiy Volodymyrovych Polunin"; Russian: Серге́й Влади́мирович Полу́нин, "Sergey Vladimirovich Polunin" ; born 20 November 1989) is a Ukrainian ballet dancer, actor and model.

Igor Belsky: Igor Dmitrievich Belsky (Russian: Игорь Дмитриевич Бельский ; 28 March 1925, Saint Petersburg, Russia – 3 July 1999, Saint Petersburg) was a Russian ballet dancer and choreographer.  After 20 years of solo work (1942–62) he became a chief choreographer of Maly Theatre (1962–73), artistic director of Kirov Ballet (1973–77), artistic director of Cairo Ballet (1977–78), chief ballet master at the Leningrad Music Hall (1979–92), and artistic director of the Vaganova Academy of Russian Ballet.

Wassily de Basil: Wassily de Basil (16 September 1888 – 27 July 1951), usually referred to as Colonel W. de Basil, was a Russian ballet impresario.

George de Cuevas: Jorge Cuevas Bartholín, known as George de Cuevas (1885 – 22 February 1961), was a Chilean-born ballet impresario and choreographer who was best known for the Grand Ballet du Marquis de Cuevas that he formed in 1944.

Oleg Polunin: Oleg Vladimirovitch Polunin (November 1914 – July 1985) was an English botanist, teacher and traveller.  He was one of three sons to the artists Vladimir (born in the Russian Empire) and Elizabeth Polunin.  All three were interested in the natural sciences, Nicholas Polunin (1909–1997) was an arctic explorer and environmentalist, and Ivan Polunin (1920–2010) was a medical doctor, photographer and ethnographist.

Supporting paragraphs: Elizabeth Polunin Sergei Diaghilev
Answer: 1872