| APA | OPKI. (2012, February 14). In Acronym Geek. Retrieved 19:52, February 14, 2012, from http://www.acronymgeek.com/OPKI |
| MLA | "OPKI." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/OPKI>. |
| MHRA | 'OPKI', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/OPKI> [accessed 14 February 2012] |
| Chicago | "OPKI", http://www.acronymgeek.com/OPKI (accessed February 14, 2012). |
| CBE/CSE | OPKI [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/OPKI. |
| Bluebook | OPKI, http://www.acronymgeek.com/OPKI (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, OPKI, http://www.acronymgeek.com/OPKI (optional description here) (as of Feb. 14, 2012, 19:52). |
| AMA | OPKI. Acronym Geek. February 14, 2012, 19:52. Available at: http://www.acronymgeek.com/OPKI. Accessed February 14, 2012, 19:52. |