| APA | PENO. (2012, February 17). In Acronym Geek. Retrieved 07:03, February 17, 2012, from http://www.acronymgeek.com/PENO |
| MLA | "PENO." Acronym Geek. (2012). Acronym Geek. 17 Feb 2012 <http://www.acronymgeek.com/PENO>. |
| MHRA | 'PENO', Acronym Geek, 17 February 2012, <http://www.acronymgeek.com/PENO> [accessed 17 February 2012] |
| Chicago | "PENO", http://www.acronymgeek.com/PENO (accessed February 17, 2012). |
| CBE/CSE | PENO [Internet]. Acronym Geek; 2012 Feb 17 [cited 2012 Feb 17]. Available from: http://www.acronymgeek.com/PENO. |
| Bluebook | PENO, http://www.acronymgeek.com/PENO (last visited February 17, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PENO, http://www.acronymgeek.com/PENO (optional description here) (as of Feb. 17, 2012, 07:03). |
| AMA | PENO. Acronym Geek. February 17, 2012, 07:03. Available at: http://www.acronymgeek.com/PENO. Accessed February 17, 2012, 07:03. |