APA (7th ed.) Citation

Haseltine, R. W., & Terry, W. E. (2009). Prelude to Space. Project Gutenberg.

Chicago Style (17th ed.) Citation

Haseltine, Robert W., and W. E. Terry. Prelude to Space. Project Gutenberg, 2009.

MLA (9th ed.) Citation

Haseltine, Robert W., and W. E. Terry. Prelude to Space. Project Gutenberg, 2009.

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