| APA | HTPO. (2012, February 11). In Acronym Geek. Retrieved 19:59, February 11, 2012, from http://www.acronymgeek.com/HTPO |
| MLA | "HTPO." Acronym Geek. (2012). Acronym Geek. 11 Feb 2012 <http://www.acronymgeek.com/HTPO>. |
| MHRA | 'HTPO', Acronym Geek, 11 February 2012, <http://www.acronymgeek.com/HTPO> [accessed 11 February 2012] |
| Chicago | "HTPO", http://www.acronymgeek.com/HTPO (accessed February 11, 2012). |
| CBE/CSE | HTPO [Internet]. Acronym Geek; 2012 Feb 11 [cited 2012 Feb 11]. Available from: http://www.acronymgeek.com/HTPO. |
| Bluebook | HTPO, http://www.acronymgeek.com/HTPO (last visited February 11, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HTPO, http://www.acronymgeek.com/HTPO (optional description here) (as of Feb. 11, 2012, 19:59). |
| AMA | HTPO. Acronym Geek. February 11, 2012, 19:59. Available at: http://www.acronymgeek.com/HTPO. Accessed February 11, 2012, 19:59. |