| APA | EI. (2012, February 9). In Acronym Geek. Retrieved 14:07, February 9, 2012, from http://www.acronymgeek.com/EI |
| MLA | "EI." Acronym Geek. (2012). Acronym Geek. 9 Feb 2012 <http://www.acronymgeek.com/EI>. |
| MHRA | 'EI', Acronym Geek, 9 February 2012, <http://www.acronymgeek.com/EI> [accessed 9 February 2012] |
| Chicago | "EI", http://www.acronymgeek.com/EI (accessed February 9, 2012). |
| CBE/CSE | EI [Internet]. Acronym Geek; 2012 Feb 9 [cited 2012 Feb 9]. Available from: http://www.acronymgeek.com/EI. |
| Bluebook | EI, http://www.acronymgeek.com/EI (last visited February 9, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, EI, http://www.acronymgeek.com/EI (optional description here) (as of Feb. 9, 2012, 14:07). |
| AMA | EI. Acronym Geek. February 9, 2012, 14:07. Available at: http://www.acronymgeek.com/EI. Accessed February 9, 2012, 14:07. |