Simon, Eric. “Der späte Ruhm des seltsamen Charles Ives” [The Be-lated Fame to the Singular Charles Ives]. HiFi--Stereophonie (January 1968) 7/1: 58-59.
Schafer, R. Murray. “Charles Ives and Perspective.” Ear Clearing: Notes for an Experimental Music Course, 31-36. Don Mills, Ontario: BMI Canada Limited, 1967.
Peterson, Thomas Elliott. “The Music of Carl Ruggles in Relation to the 20th Century.” In The Music of Carl Ruggles. Ph.D. diss., University of Washington, 1967.