APA (7th ed.) Citation

Hornaday, W. T. (1927). Official guide book to the New York zoological park. New York zoological society.

Chicago Style (17th ed.) Citation

Hornaday, William T. Official Guide Book to the New York Zoological Park. New York: New York zoological society, 1927.

MLA (9th ed.) Citation

Hornaday, William T. Official Guide Book to the New York Zoological Park. New York zoological society, 1927.