| APA | OPG. (2012, February 14). In Acronym Geek. Retrieved 09:45, February 14, 2012, from http://www.acronymgeek.com/OPG |
| MLA | "OPG." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/OPG>. |
| MHRA | 'OPG', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/OPG> [accessed 14 February 2012] |
| Chicago | "OPG", http://www.acronymgeek.com/OPG (accessed February 14, 2012). |
| CBE/CSE | OPG [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/OPG. |
| Bluebook | OPG, http://www.acronymgeek.com/OPG (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, OPG, http://www.acronymgeek.com/OPG (optional description here) (as of Feb. 14, 2012, 09:45). |
| AMA | OPG. Acronym Geek. February 14, 2012, 09:45. Available at: http://www.acronymgeek.com/OPG. Accessed February 14, 2012, 09:45. |