From the Bassoon-Family Fingering Companion by Terry B. Ewell - Groeling, Charles R. "Cultivating Bassoonists." The Instrumentalist 47/1 (August 1992): 50. Cooper p. 226. - Moritz, Frederick. "A Dissertation on the Use of Alternate Fingerings for Some of the High Register Notes on the Heckel and Heckel-Type Bassoons." The Double Reed 8/3 (Winter 1985): 28, 29, 32