| APA | PI. (2012, February 14). In Acronym Geek. Retrieved 06:14, February 14, 2012, from http://www.acronymgeek.com/PI |
| MLA | "PI." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/PI>. |
| MHRA | 'PI', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/PI> [accessed 14 February 2012] |
| Chicago | "PI", http://www.acronymgeek.com/PI (accessed February 14, 2012). |
| CBE/CSE | PI [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/PI. |
| Bluebook | PI, http://www.acronymgeek.com/PI (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PI, http://www.acronymgeek.com/PI (optional description here) (as of Feb. 14, 2012, 06:14). |
| AMA | PI. Acronym Geek. February 14, 2012, 06:14. Available at: http://www.acronymgeek.com/PI. Accessed February 14, 2012, 06:14. |