Cite Them Right 11th edition - Harvard

Joe Leo and Joe Leo (2009) The Well-Grounded Rubyist.

Chicago Manual of Style 17th edition (full note)

Joe Leo, and Joe Leo. The Well-Grounded Rubyist.

American Psychological Association 7th edition

Joe Leo, & Joe Leo. (2009). The Well-Grounded Rubyist.

Modern Language Association 9th edition

Joe Leo, and Joe Leo. The Well-Grounded Rubyist. 2009.

ISO-690 (author-date, Deutsch)

JOE LEO and JOE LEO, 2009. The Well-Grounded Rubyist

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