APA (7th ed.) Citation

Walton, F. D. The Flying Machine Boys on Duty; Or, The Clue Above the Clouds.

Chicago Style (17th ed.) Citation

Walton, Frank; Davis. The Flying Machine Boys on Duty; Or, The Clue Above the Clouds.

MLA (9th ed.) Citation

Walton, Frank; Davis. The Flying Machine Boys on Duty; Or, The Clue Above the Clouds.

Warning: These citations may not always be 100% accurate.