Southwest Airways, Inc.. "Southwest Airways annual report 1956." Delta Flight Museum. 1957, https://dlg.galileo.usg.edu/do:delta_pca-ar_pca-ar-1956.

Southwest Airways, Inc. (1957). Southwest Airways annual report 1956. Retrieved from https://dlg.galileo.usg.edu/do:delta_pca-ar_pca-ar-1956

Southwest Airways, Inc.. "Southwest Airways annual report 1956." 1957. June 18, 2025. https://dlg.galileo.usg.edu/do:delta_pca-ar_pca-ar-1956.