Colby, Frank Moore, ed. The New International Year Book (for 1919), p. 657 (1920)(reporting that Boyle set a new American women's record of 64 feet in the plunge in 1919)
Sinclair, Archibald and Henry, William. Swimming, p. 405 (1916 edition)
(20 March 1920). Swimming Records Made, The New York Times (reporting that Boyle's 66 feet was both an American record and a new world's record, beating the former record of 65 feet 10 inches held by Helen Nolan of Detroit)
(13 October 1913). College Swimmers Meet, The New York Times ("An attempt was also made to have the plunge for distance abandoned in favor of a fifty-yard back-stroke race, but the motion did not go through.")