APA (7th ed.) Citation

Pennell, E. R., & Pennell, J. (2011). Our Philadelphia. Project Gutenberg.

Chicago Style (17th ed.) Citation

Pennell, Elizabeth Robins, and Joseph Pennell. Our Philadelphia. Project Gutenberg, 2011.

MLA (9th ed.) Citation

Pennell, Elizabeth Robins, and Joseph Pennell. Our Philadelphia. Project Gutenberg, 2011.

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