APA (7th ed.) Citation

Hale, G. E., & Nicholson, S. B. (1938). Magnetic observation of sunspots, 1917-1924 ... Carnegie institution of Washington.

Chicago Style (17th ed.) Citation

Hale, George Ellery, and Seth Barnes Nicholson. Magnetic Observation of Sunspots, 1917-1924 ... Washington, D.C.: Carnegie institution of Washington, 1938.

MLA (9th ed.) Citation

Hale, George Ellery, and Seth Barnes Nicholson. Magnetic Observation of Sunspots, 1917-1924 ... Carnegie institution of Washington, 1938.