APA (7th ed.) Citation

Keen, M. L., & Sweet, D. (1961). The how and why wonder book of the human body. Wonder Books.

Chicago Style (17th ed.) Citation

Keen, Martin L., and Darrell Sweet. The How and Why Wonder Book of the Human Body. New York: Wonder Books, 1961.

MLA (9th ed.) Citation

Keen, Martin L., and Darrell Sweet. The How and Why Wonder Book of the Human Body. Wonder Books, 1961.