APA (7th ed.) Citation

Burgess, E. W., & Park, R. E. (2009). Introduction to the Science of Sociology. Project Gutenberg.

Chicago Style (17th ed.) Citation

Burgess, E. W., and Robert Ezra Park. Introduction to the Science of Sociology. Project Gutenberg, 2009.

MLA (9th ed.) Citation

Burgess, E. W., and Robert Ezra Park. Introduction to the Science of Sociology. Project Gutenberg, 2009.

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