APA (7th ed.) Citation

Hornaday, W. T. (1911). Popular official guide to the New York zoological park (11th ed.). New York zoological society.

Chicago Style (17th ed.) Citation

Hornaday, William T. Popular Official Guide to the New York Zoological Park. 11th ed. New York: New York zoological society, 1911.

MLA (9th ed.) Citation

Hornaday, William T. Popular Official Guide to the New York Zoological Park. 11th ed. New York zoological society, 1911.