| APA | HKOS. (2012, February 15). In Acronym Geek. Retrieved 09:39, February 15, 2012, from http://www.acronymgeek.com/HKOS |
| MLA | "HKOS." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/HKOS>. |
| MHRA | 'HKOS', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/HKOS> [accessed 15 February 2012] |
| Chicago | "HKOS", http://www.acronymgeek.com/HKOS (accessed February 15, 2012). |
| CBE/CSE | HKOS [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/HKOS. |
| Bluebook | HKOS, http://www.acronymgeek.com/HKOS (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HKOS, http://www.acronymgeek.com/HKOS (optional description here) (as of Feb. 15, 2012, 09:39). |
| AMA | HKOS. Acronym Geek. February 15, 2012, 09:39. Available at: http://www.acronymgeek.com/HKOS. Accessed February 15, 2012, 09:39. |