| APA | HKOP. (2012, February 16). In Acronym Geek. Retrieved 23:51, February 16, 2012, from http://www.acronymgeek.com/HKOP |
| MLA | "HKOP." Acronym Geek. (2012). Acronym Geek. 16 Feb 2012 <http://www.acronymgeek.com/HKOP>. |
| MHRA | 'HKOP', Acronym Geek, 16 February 2012, <http://www.acronymgeek.com/HKOP> [accessed 16 February 2012] |
| Chicago | "HKOP", http://www.acronymgeek.com/HKOP (accessed February 16, 2012). |
| CBE/CSE | HKOP [Internet]. Acronym Geek; 2012 Feb 16 [cited 2012 Feb 16]. Available from: http://www.acronymgeek.com/HKOP. |
| Bluebook | HKOP, http://www.acronymgeek.com/HKOP (last visited February 16, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HKOP, http://www.acronymgeek.com/HKOP (optional description here) (as of Feb. 16, 2012, 23:51). |
| AMA | HKOP. Acronym Geek. February 16, 2012, 23:51. Available at: http://www.acronymgeek.com/HKOP. Accessed February 16, 2012, 23:51. |