APA (7th ed.) Citation

Lehmer, D. N. (2005). An Elementary Course in Synthetic Projective Geometry. Project Gutenberg.

Chicago Style (17th ed.) Citation

Lehmer, Derrick Norman. An Elementary Course in Synthetic Projective Geometry. Project Gutenberg, 2005.

MLA (9th ed.) Citation

Lehmer, Derrick Norman. An Elementary Course in Synthetic Projective Geometry. Project Gutenberg, 2005.

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