| APA | PENS. (2012, February 15). In Acronym Geek. Retrieved 18:55, February 15, 2012, from http://www.acronymgeek.com/PENS |
| MLA | "PENS." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/PENS>. |
| MHRA | 'PENS', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/PENS> [accessed 15 February 2012] |
| Chicago | "PENS", http://www.acronymgeek.com/PENS (accessed February 15, 2012). |
| CBE/CSE | PENS [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/PENS. |
| Bluebook | PENS, http://www.acronymgeek.com/PENS (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PENS, http://www.acronymgeek.com/PENS (optional description here) (as of Feb. 15, 2012, 18:55). |
| AMA | PENS. Acronym Geek. February 15, 2012, 18:55. Available at: http://www.acronymgeek.com/PENS. Accessed February 15, 2012, 18:55. |