| APA | HHDO. (2012, February 14). In Acronym Geek. Retrieved 18:35, February 14, 2012, from http://www.acronymgeek.com/HHDO |
| MLA | "HHDO." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/HHDO>. |
| MHRA | 'HHDO', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/HHDO> [accessed 14 February 2012] |
| Chicago | "HHDO", http://www.acronymgeek.com/HHDO (accessed February 14, 2012). |
| CBE/CSE | HHDO [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/HHDO. |
| Bluebook | HHDO, http://www.acronymgeek.com/HHDO (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HHDO, http://www.acronymgeek.com/HHDO (optional description here) (as of Feb. 14, 2012, 18:35). |
| AMA | HHDO. Acronym Geek. February 14, 2012, 18:35. Available at: http://www.acronymgeek.com/HHDO. Accessed February 14, 2012, 18:35. |