| APA | PFO. (2012, February 8). In Acronym Geek. Retrieved 19:53, February 8, 2012, from http://www.acronymgeek.com/PFO |
| MLA | "PFO." Acronym Geek. (2012). Acronym Geek. 8 Feb 2012 <http://www.acronymgeek.com/PFO>. |
| MHRA | 'PFO', Acronym Geek, 8 February 2012, <http://www.acronymgeek.com/PFO> [accessed 8 February 2012] |
| Chicago | "PFO", http://www.acronymgeek.com/PFO (accessed February 8, 2012). |
| CBE/CSE | PFO [Internet]. Acronym Geek; 2012 Feb 8 [cited 2012 Feb 8]. Available from: http://www.acronymgeek.com/PFO. |
| Bluebook | PFO, http://www.acronymgeek.com/PFO (last visited February 8, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, PFO, http://www.acronymgeek.com/PFO (optional description here) (as of Feb. 8, 2012, 19:53). |
| AMA | PFO. Acronym Geek. February 8, 2012, 19:53. Available at: http://www.acronymgeek.com/PFO. Accessed February 8, 2012, 19:53. |