1. J. Pfaff
, “
Flute,” U.S. patent No. 17,054 (April 14, 1857).
2. K. F. W. Guenther
, “
Flute,” U.S. patent No. 444,830 (January 20, 1891).
3. C. T. Giorgi
, “
Flute,” U.S. patent No. 594,735 (November 30, 1897).
4. S. Wesley, Sr.
, “
End blown free air-reed flute,” U.S. patent No. 5,014,585 (May 14, 1991) and “End blown flute with standard keying,” U.S. patent No. 3,888,154 (June 10, 1975).
5. M. Visser
, “
Transversely-blown vertical and swan-angled headjoints,” https://www.flutelab.com/swan_neck/ and https://www.flutelab.com/vertical/ (Last viewed February 8, 2021).