| APA | PTR. (2012, February 4). In Acronym Geek. Retrieved 11:17, February 4, 2012, from http://www.acronymgeek.com/PTR |
| MLA | "PTR." Acronym Geek. (2012). Acronym Geek. 4 Feb 2012 <http://www.acronymgeek.com/PTR>. |
| MHRA | 'PTR', Acronym Geek, 4 February 2012, <http://www.acronymgeek.com/PTR> [accessed 4 February 2012] |
| Chicago | "PTR", http://www.acronymgeek.com/PTR (accessed February 4, 2012). |
| CBE/CSE | PTR [Internet]. Acronym Geek; 2012 Feb 4 [cited 2012 Feb 4]. Available from: http://www.acronymgeek.com/PTR. |
| Bluebook | PTR, http://www.acronymgeek.com/PTR (last visited February 4, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PTR, http://www.acronymgeek.com/PTR (optional description here) (as of Feb. 4, 2012, 11:17). |
| AMA | PTR. Acronym Geek. February 4, 2012, 11:17. Available at: http://www.acronymgeek.com/PTR. Accessed February 4, 2012, 11:17. |