APA (7th ed.) Citation

Funk, W. J., & Lewis, N. (1942). 30 days to a more powerful vocabulary. Wilfred Funk, Inc.

Chicago Style (17th ed.) Citation

Funk, Wilfred J., and Norman Lewis. 30 Days to a More Powerful Vocabulary. New York: Wilfred Funk, Inc, 1942.

MLA (9th ed.) Citation

Funk, Wilfred J., and Norman Lewis. 30 Days to a More Powerful Vocabulary. Wilfred Funk, Inc, 1942.