APA (7th ed.) Citation

Hubble, E. P. (1958). The realm of the nebulae. Dover Publications.

Chicago Style (17th ed.) Citation

Hubble, Edwin Powell. The Realm of the Nebulae. New York: Dover Publications, 1958.

MLA (9th ed.) Citation

Hubble, Edwin Powell. The Realm of the Nebulae. Dover Publications, 1958.

Warning: These citations may not always be 100% accurate.