| APA | HLDO. (2012, February 15). In Acronym Geek. Retrieved 23:57, February 15, 2012, from http://www.acronymgeek.com/HLDO |
| MLA | "HLDO." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/HLDO>. |
| MHRA | 'HLDO', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/HLDO> [accessed 15 February 2012] |
| Chicago | "HLDO", http://www.acronymgeek.com/HLDO (accessed February 15, 2012). |
| CBE/CSE | HLDO [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/HLDO. |
| Bluebook | HLDO, http://www.acronymgeek.com/HLDO (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HLDO, http://www.acronymgeek.com/HLDO (optional description here) (as of Feb. 15, 2012, 23:57). |
| AMA | HLDO. Acronym Geek. February 15, 2012, 23:57. Available at: http://www.acronymgeek.com/HLDO. Accessed February 15, 2012, 23:57. |