| APA | OPUK. (2012, February 15). In Acronym Geek. Retrieved 19:49, February 15, 2012, from http://www.acronymgeek.com/OPUK |
| MLA | "OPUK." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/OPUK>. |
| MHRA | 'OPUK', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/OPUK> [accessed 15 February 2012] |
| Chicago | "OPUK", http://www.acronymgeek.com/OPUK (accessed February 15, 2012). |
| CBE/CSE | OPUK [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/OPUK. |
| Bluebook | OPUK, http://www.acronymgeek.com/OPUK (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, OPUK, http://www.acronymgeek.com/OPUK (optional description here) (as of Feb. 15, 2012, 19:49). |
| AMA | OPUK. Acronym Geek. February 15, 2012, 19:49. Available at: http://www.acronymgeek.com/OPUK. Accessed February 15, 2012, 19:49. |