APA (7th ed.) Citation

Harrington, D., & Owings, C. W. (1929). Safety letters. [publisher not identified].

Chicago Style (17th ed.) Citation

Harrington, D., and C. W. Owings. Safety Letters. Washington, D.C.: [publisher not identified], 1929.

MLA (9th ed.) Citation

Harrington, D., and C. W. Owings. Safety Letters. [publisher not identified], 1929.