| APA | OEI. (2012, February 14). In Acronym Geek. Retrieved 07:40, February 14, 2012, from http://www.acronymgeek.com/OEI |
| MLA | "OEI." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/OEI>. |
| MHRA | 'OEI', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/OEI> [accessed 14 February 2012] |
| Chicago | "OEI", http://www.acronymgeek.com/OEI (accessed February 14, 2012). |
| CBE/CSE | OEI [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/OEI. |
| Bluebook | OEI, http://www.acronymgeek.com/OEI (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, OEI, http://www.acronymgeek.com/OEI (optional description here) (as of Feb. 14, 2012, 07:40). |
| AMA | OEI. Acronym Geek. February 14, 2012, 07:40. Available at: http://www.acronymgeek.com/OEI. Accessed February 14, 2012, 07:40. |