Marble, Frank E.; Ritter, William K. & Miller, Mahlon A. Effect of the NACA Injection Impeller on the Mixture Distribution of a Double-Row Radial Aircraft Engine, report, May 1946; (https://digital.library.unt.edu/ark:/67531/metadc54942/m1/1/: accessed October 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .