APA (7th ed.) Citation

Riley, J. W., Christy, H. C., & Keep, V. (2008). An Old Sweetheart of Mine. Project Gutenberg.

Chicago Style (17th ed.) Citation

Riley, James Whitcomb, Howard Chandler Christy, and Virginia Keep. An Old Sweetheart of Mine. Project Gutenberg, 2008.

MLA (9th ed.) Citation

Riley, James Whitcomb, et al. An Old Sweetheart of Mine. Project Gutenberg, 2008.

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