| APA | HPBO. (2012, February 15). In Acronym Geek. Retrieved 14:09, February 15, 2012, from http://www.acronymgeek.com/HPBO |
| MLA | "HPBO." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/HPBO>. |
| MHRA | 'HPBO', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/HPBO> [accessed 15 February 2012] |
| Chicago | "HPBO", http://www.acronymgeek.com/HPBO (accessed February 15, 2012). |
| CBE/CSE | HPBO [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/HPBO. |
| Bluebook | HPBO, http://www.acronymgeek.com/HPBO (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HPBO, http://www.acronymgeek.com/HPBO (optional description here) (as of Feb. 15, 2012, 14:09). |
| AMA | HPBO. Acronym Geek. February 15, 2012, 14:09. Available at: http://www.acronymgeek.com/HPBO. Accessed February 15, 2012, 14:09. |