From the Bassoon-Family Fingering Companion by Terry B. Ewell - Groeling, Charles R. "Cultivating Bassoonists." The Instrumentalist 47/1 (August 1992): 50. Swanson, Robert. "Pictorial Bassoon Fingerings." Woodwind Magazine 4/1 (September 1951): 9. Turkovic, Milan. In Klimko, Ronald. Bassoon Performance Practices and Teaching in the United States and Canada. Idaho: University of Idaho, 1974, p. 70. Cooper p. 182 (no whisper key).