The piano variations The People United will Never be Defeated by Rzewski contains many modern piano performance techniques and skills. The difficulties of these techniques and skills in these enormous variations are far beyond the boundaries of traditional piano performance techniques and skills. This analysis will give a specific classification for these modern piano performance techniques and skills in order to provide a more comprehensive guide for the piano performers.
 Deng Liang. (February 01, 2017). Reviews on Rzewski’s Leftist Political Piano Variations: ‘The People United Will Never Be Defeated’. Accelerando: Bjmd, 2, 2.)
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 Rzewski, F., Raat, R. ., & Naxos Digital Services. (2008). RZEWSKI: The People United Will Never Be Defeated. Hong Kong: Naxos Digital Services Ltd. [Online] Available: http://www.naxos.com/mainsite/blurbs_reviews.asp?item_code=8.559360&catNum=559360&filetype=About%20this%20Recording&language=English, (Accessed 01/05/2018).
 Crumb, G. (1972). [Eleven echoes of autumn, 1965]: Eleven echoes of autumn, 1965 : violin, alto flute, clarinet and piano. New York: Peters.
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 Rzewski, F., Rzewski, F., Adznikolov, T., & Miami International Piano Festival. (2008). Frederic Rzewski, composer & pianist: The people united will never be defeated! : 36 variations on ¡El pueblo unido jamás será vencido!. Pleasantville, NY: VAI. Organizational Design of BIg data and analytics teams.