Delta Air Lines System Timetable April 1, 1991
MLA
Delta Air Lines, Inc.. "Delta Air Lines System Timetable April 1, 1991." Delta Flight Museum. 1991-04-01, https://dlg.galileo.usg.edu/do:delta_dal-tt_dal-tt-19910401.
APA
Delta Air Lines, Inc. (1991-04-01). Delta Air Lines System Timetable April 1, 1991. Retrieved from https://dlg.galileo.usg.edu/do:delta_dal-tt_dal-tt-19910401
Chicago
Delta Air Lines, Inc.. "Delta Air Lines System Timetable April 1, 1991." 1991-04-01. April 30, 2026. https://dlg.galileo.usg.edu/do:delta_dal-tt_dal-tt-19910401.
