| APA | HPKI. (2012, February 14). In Acronym Geek. Retrieved 00:33, February 14, 2012, from http://www.acronymgeek.com/HPKI |
| MLA | "HPKI." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/HPKI>. |
| MHRA | 'HPKI', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/HPKI> [accessed 14 February 2012] |
| Chicago | "HPKI", http://www.acronymgeek.com/HPKI (accessed February 14, 2012). |
| CBE/CSE | HPKI [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/HPKI. |
| Bluebook | HPKI, http://www.acronymgeek.com/HPKI (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, HPKI, http://www.acronymgeek.com/HPKI (optional description here) (as of Feb. 14, 2012, 00:33). |
| AMA | HPKI. Acronym Geek. February 14, 2012, 00:33. Available at: http://www.acronymgeek.com/HPKI. Accessed February 14, 2012, 00:33. |