APA (7th ed.) Citation

Smith, E. E., & Emshwiller, E. (2010). Helpfully Yours. Project Gutenberg.

Chicago Style (17th ed.) Citation

Smith, Evelyn E., and Ed Emshwiller. Helpfully Yours. Project Gutenberg, 2010.

MLA (9th ed.) Citation

Smith, Evelyn E., and Ed Emshwiller. Helpfully Yours. Project Gutenberg, 2010.

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