| APA | HAPO. (2012, February 16). In Acronym Geek. Retrieved 07:27, February 16, 2012, from http://www.acronymgeek.com/HAPO |
| MLA | "HAPO." Acronym Geek. (2012). Acronym Geek. 16 Feb 2012 <http://www.acronymgeek.com/HAPO>. |
| MHRA | 'HAPO', Acronym Geek, 16 February 2012, <http://www.acronymgeek.com/HAPO> [accessed 16 February 2012] |
| Chicago | "HAPO", http://www.acronymgeek.com/HAPO (accessed February 16, 2012). |
| CBE/CSE | HAPO [Internet]. Acronym Geek; 2012 Feb 16 [cited 2012 Feb 16]. Available from: http://www.acronymgeek.com/HAPO. |
| Bluebook | HAPO, http://www.acronymgeek.com/HAPO (last visited February 16, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HAPO, http://www.acronymgeek.com/HAPO (optional description here) (as of Feb. 16, 2012, 07:27). |
| AMA | HAPO. Acronym Geek. February 16, 2012, 07:27. Available at: http://www.acronymgeek.com/HAPO. Accessed February 16, 2012, 07:27. |