| APA | HHEO. (2012, February 15). In Acronym Geek. Retrieved 10:12, February 15, 2012, from http://www.acronymgeek.com/HHEO |
| MLA | "HHEO." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/HHEO>. |
| MHRA | 'HHEO', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/HHEO> [accessed 15 February 2012] |
| Chicago | "HHEO", http://www.acronymgeek.com/HHEO (accessed February 15, 2012). |
| CBE/CSE | HHEO [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/HHEO. |
| Bluebook | HHEO, http://www.acronymgeek.com/HHEO (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HHEO, http://www.acronymgeek.com/HHEO (optional description here) (as of Feb. 15, 2012, 10:12). |
| AMA | HHEO. Acronym Geek. February 15, 2012, 10:12. Available at: http://www.acronymgeek.com/HHEO. Accessed February 15, 2012, 10:12. |