| APA | HHDH. (2012, February 14). In Acronym Geek. Retrieved 13:28, February 14, 2012, from http://www.acronymgeek.com/HHDH |
| MLA | "HHDH." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/HHDH>. |
| MHRA | 'HHDH', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/HHDH> [accessed 14 February 2012] |
| Chicago | "HHDH", http://www.acronymgeek.com/HHDH (accessed February 14, 2012). |
| CBE/CSE | HHDH [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/HHDH. |
| Bluebook | HHDH, http://www.acronymgeek.com/HHDH (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HHDH, http://www.acronymgeek.com/HHDH (optional description here) (as of Feb. 14, 2012, 13:28). |
| AMA | HHDH. Acronym Geek. February 14, 2012, 13:28. Available at: http://www.acronymgeek.com/HHDH. Accessed February 14, 2012, 13:28. |