| APA | HLEO. (2012, February 16). In Acronym Geek. Retrieved 23:41, February 16, 2012, from http://www.acronymgeek.com/HLEO |
| MLA | "HLEO." Acronym Geek. (2012). Acronym Geek. 16 Feb 2012 <http://www.acronymgeek.com/HLEO>. |
| MHRA | 'HLEO', Acronym Geek, 16 February 2012, <http://www.acronymgeek.com/HLEO> [accessed 16 February 2012] |
| Chicago | "HLEO", http://www.acronymgeek.com/HLEO (accessed February 16, 2012). |
| CBE/CSE | HLEO [Internet]. Acronym Geek; 2012 Feb 16 [cited 2012 Feb 16]. Available from: http://www.acronymgeek.com/HLEO. |
| Bluebook | HLEO, http://www.acronymgeek.com/HLEO (last visited February 16, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HLEO, http://www.acronymgeek.com/HLEO (optional description here) (as of Feb. 16, 2012, 23:41). |
| AMA | HLEO. Acronym Geek. February 16, 2012, 23:41. Available at: http://www.acronymgeek.com/HLEO. Accessed February 16, 2012, 23:41. |