| APA | H.O.. (2012, February 16). In Acronym Geek. Retrieved 03:02, February 16, 2012, from http://www.acronymgeek.com/H.O. |
| MLA | "H.O.." Acronym Geek. (2012). Acronym Geek. 16 Feb 2012 <http://www.acronymgeek.com/H.O.>. |
| MHRA | 'H.O.', Acronym Geek, 16 February 2012, <http://www.acronymgeek.com/H.O.> [accessed 16 February 2012] |
| Chicago | "H.O.", http://www.acronymgeek.com/H.O. (accessed February 16, 2012). |
| CBE/CSE | H.O. [Internet]. Acronym Geek; 2012 Feb 16 [cited 2012 Feb 16]. Available from: http://www.acronymgeek.com/H.O.. |
| Bluebook | H.O., http://www.acronymgeek.com/H.O. (last visited February 16, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, H.O., http://www.acronymgeek.com/H.O. (optional description here) (as of Feb. 16, 2012, 03:02). |
| AMA | H.O.. Acronym Geek. February 16, 2012, 03:02. Available at: http://www.acronymgeek.com/H.O.. Accessed February 16, 2012, 03:02. |