| APA | OPXN. (2012, February 14). In Acronym Geek. Retrieved 18:01, February 14, 2012, from http://www.acronymgeek.com/OPXN |
| MLA | "OPXN." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/OPXN>. |
| MHRA | 'OPXN', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/OPXN> [accessed 14 February 2012] |
| Chicago | "OPXN", http://www.acronymgeek.com/OPXN (accessed February 14, 2012). |
| CBE/CSE | OPXN [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/OPXN. |
| Bluebook | OPXN, http://www.acronymgeek.com/OPXN (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, OPXN, http://www.acronymgeek.com/OPXN (optional description here) (as of Feb. 14, 2012, 18:01). |
| AMA | OPXN. Acronym Geek. February 14, 2012, 18:01. Available at: http://www.acronymgeek.com/OPXN. Accessed February 14, 2012, 18:01. |