| APA | PENI. (2012, February 17). In Acronym Geek. Retrieved 06:44, February 17, 2012, from http://www.acronymgeek.com/PENI |
| MLA | "PENI." Acronym Geek. (2012). Acronym Geek. 17 Feb 2012 <http://www.acronymgeek.com/PENI>. |
| MHRA | 'PENI', Acronym Geek, 17 February 2012, <http://www.acronymgeek.com/PENI> [accessed 17 February 2012] |
| Chicago | "PENI", http://www.acronymgeek.com/PENI (accessed February 17, 2012). |
| CBE/CSE | PENI [Internet]. Acronym Geek; 2012 Feb 17 [cited 2012 Feb 17]. Available from: http://www.acronymgeek.com/PENI. |
| Bluebook | PENI, http://www.acronymgeek.com/PENI (last visited February 17, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PENI, http://www.acronymgeek.com/PENI (optional description here) (as of Feb. 17, 2012, 06:44). |
| AMA | PENI. Acronym Geek. February 17, 2012, 06:44. Available at: http://www.acronymgeek.com/PENI. Accessed February 17, 2012, 06:44. |