When Sergeyev died in Nice, France on 23 June 1951 the notations passed on for a brief time to a Russian associate of his, from whom Mona Inglesby purchased them, continuing to stage his productions with International Ballet until its closure in 1953. Inglesby, through the London theatrical dealer Ifan Kyrle Fletcher, sold the Petipa "Swan Lake" notation to Harvard University in 1967, followed by the rest of the notations in 1969, for a sum claimed to be around £6,000. Today the collection is known officially as the "Nikolai Sergeev Dance Notations and Music Scores for Ballets", though it is commonly referred to simply as "The Sergeyev Collection". For some time the notations were useless, as no one in the world had any knowledge of how to read Stepanov's method. It was not until Stepanov's original primer was found in the archives of the Mariinsky Theatre that the notations were able to be deciphered.