APA (7th ed.) Citation

Merrill, P. W. (1938). The nature of variable stars. Macmillan.

Chicago Style (17th ed.) Citation

Merrill, Paul W. The Nature of Variable Stars. New York: Macmillan, 1938.

MLA (9th ed.) Citation

Merrill, Paul W. The Nature of Variable Stars. Macmillan, 1938.