1The Official George Crumb website, USA, 2013, retrieved http: //www.georgecrumb.net, 06/2013.
2Deng Liang, Performance Techniques in Modern Piano Music, Pro- Quest, UMI Dissertations Publishing, Ann Arbor, MI, USA, 2011-2012.
3Gillespie, Don C. George Crumb, profile of a composer. Vol. 2. CF Peters Corp, 1986.
4Crumb, George, Eleven Echoes of Autumn: 1965. Composers Recordings, 1969.
5Crumb, George, Eleven Echoes of Autumn (Echoes I), Contempo- rary Small Ensemble. For Violin, Alto-Flute, Clarinet, Piano, Com- posed 1965, C.F. Peters, USA, 1972.
6Goodman, Jonathan Micheal. "CHAMBER STUDY TO PULITZER PRIZE: A COMPARISON OF GEORGE CRUMB'S ELEVEN E- CHOES OF AUTUMN, 1965 (ECHOES I) AND ECHOES OF TIME AND RIVER (ECHOES I1)." (2011).