| APA | PTO. (2012, February 14). In Acronym Geek. Retrieved 11:34, February 14, 2012, from http://www.acronymgeek.com/PTO |
| MLA | "PTO." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/PTO>. |
| MHRA | 'PTO', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/PTO> [accessed 14 February 2012] |
| Chicago | "PTO", http://www.acronymgeek.com/PTO (accessed February 14, 2012). |
| CBE/CSE | PTO [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/PTO. |
| Bluebook | PTO, http://www.acronymgeek.com/PTO (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PTO, http://www.acronymgeek.com/PTO (optional description here) (as of Feb. 14, 2012, 11:34). |
| AMA | PTO. Acronym Geek. February 14, 2012, 11:34. Available at: http://www.acronymgeek.com/PTO. Accessed February 14, 2012, 11:34. |