Malvestuto, Frank S., Jr. Method of Estimating the Minimum Size of a Tail or Wing-Tip Parachute for Emergency Spin Recovery of an Airplane, report, October 27, 1948; (https://digital.library.unt.edu/ark:/67531/metadc62840/m1/1/: accessed January 17, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .