APA (7th ed.) Citation

Struve, O., & Zebergs, V. (1962). Astronomy of the 20th century. Macmillan.

Chicago Style (17th ed.) Citation

Struve, Otto, and Velta Zebergs. Astronomy of the 20th Century. New York: Macmillan, 1962.

MLA (9th ed.) Citation

Struve, Otto, and Velta Zebergs. Astronomy of the 20th Century. Macmillan, 1962.