| APA | OPU. (2012, February 14). In Acronym Geek. Retrieved 04:24, February 14, 2012, from http://www.acronymgeek.com/OPU |
| MLA | "OPU." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/OPU>. |
| MHRA | 'OPU', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/OPU> [accessed 14 February 2012] |
| Chicago | "OPU", http://www.acronymgeek.com/OPU (accessed February 14, 2012). |
| CBE/CSE | OPU [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/OPU. |
| Bluebook | OPU, http://www.acronymgeek.com/OPU (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, OPU, http://www.acronymgeek.com/OPU (optional description here) (as of Feb. 14, 2012, 04:24). |
| AMA | OPU. Acronym Geek. February 14, 2012, 04:24. Available at: http://www.acronymgeek.com/OPU. Accessed February 14, 2012, 04:24. |