D2-A2. Christlieb, Don. Pictoral Fingerings for Bassoon. Published by author, 1966, p. 31. Timm, Everett LeRoy. The Woodwinds; Performance and Instructional Techniques. Boston: Allyn and Bacon, 1964, p. 179.
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Heckel-System (German) Bassoon Trills and Shakes by Note Names