APA (7th ed.) Citation

Unknown. (2013). Measuring Tools Machinery's Reference Series Number 21. Project Gutenberg.

Chicago Style (17th ed.) Citation

Unknown. Measuring Tools Machinery's Reference Series Number 21. Project Gutenberg, 2013.

MLA (9th ed.) Citation

Unknown. Measuring Tools Machinery's Reference Series Number 21. Project Gutenberg, 2013.

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