| APA | PTBO. (2012, February 15). In Acronym Geek. Retrieved 18:34, February 15, 2012, from http://www.acronymgeek.com/PTBO |
| MLA | "PTBO." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/PTBO>. |
| MHRA | 'PTBO', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/PTBO> [accessed 15 February 2012] |
| Chicago | "PTBO", http://www.acronymgeek.com/PTBO (accessed February 15, 2012). |
| CBE/CSE | PTBO [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/PTBO. |
| Bluebook | PTBO, http://www.acronymgeek.com/PTBO (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PTBO, http://www.acronymgeek.com/PTBO (optional description here) (as of Feb. 15, 2012, 18:34). |
| AMA | PTBO. Acronym Geek. February 15, 2012, 18:34. Available at: http://www.acronymgeek.com/PTBO. Accessed February 15, 2012, 18:34. |