| APA | HVO. (2012, February 14). In Acronym Geek. Retrieved 20:39, February 14, 2012, from http://www.acronymgeek.com/HVO |
| MLA | "HVO." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/HVO>. |
| MHRA | 'HVO', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/HVO> [accessed 14 February 2012] |
| Chicago | "HVO", http://www.acronymgeek.com/HVO (accessed February 14, 2012). |
| CBE/CSE | HVO [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/HVO. |
| Bluebook | HVO, http://www.acronymgeek.com/HVO (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HVO, http://www.acronymgeek.com/HVO (optional description here) (as of Feb. 14, 2012, 20:39). |
| AMA | HVO. Acronym Geek. February 14, 2012, 20:39. Available at: http://www.acronymgeek.com/HVO. Accessed February 14, 2012, 20:39. |