APA (7th ed.) Citation

Boys, C. V. (2010). Soap-Bubbles and the Forces Which Mould Them. Project Gutenberg.

Chicago Style (17th ed.) Citation

Boys, C. V. Soap-Bubbles and the Forces Which Mould Them. Project Gutenberg, 2010.

MLA (9th ed.) Citation

Boys, C. V. Soap-Bubbles and the Forces Which Mould Them. Project Gutenberg, 2010.

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