BORROFF, Edith. "Crumb, George." In: The New Grove Dictionary of American Music. H. Wiley Hitchcock and Stanley Sadie, eds. London and New York: Macmillan, 1986.

MORTON, Brian & COLLINS, Pamela (eds). Contemporary Composers. St. James Press, 1992. ISBN 1558620850
[Buy this book at Amazon.com]

PEARLMAN, Leonard A. "Crumb, George (Henry)." In: The New Grove Dictionary of Music and Musicians. Sadie, S., ed. London and New York: Macmillan, 1980.

George Crumb Wikipedia entry