| APA | OPAS. (2012, February 15). In Acronym Geek. Retrieved 04:30, February 15, 2012, from http://www.acronymgeek.com/OPAS |
| MLA | "OPAS." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/OPAS>. |
| MHRA | 'OPAS', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/OPAS> [accessed 15 February 2012] |
| Chicago | "OPAS", http://www.acronymgeek.com/OPAS (accessed February 15, 2012). |
| CBE/CSE | OPAS [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/OPAS. |
| Bluebook | OPAS, http://www.acronymgeek.com/OPAS (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, OPAS, http://www.acronymgeek.com/OPAS (optional description here) (as of Feb. 15, 2012, 04:30). |
| AMA | OPAS. Acronym Geek. February 15, 2012, 04:30. Available at: http://www.acronymgeek.com/OPAS. Accessed February 15, 2012, 04:30. |