| APA | E4. (2012, February 10). In Acronym Geek. Retrieved 09:39, February 10, 2012, from http://www.acronymgeek.com/E4 |
| MLA | "E4." Acronym Geek. (2012). Acronym Geek. 10 Feb 2012 <http://www.acronymgeek.com/E4>. |
| MHRA | 'E4', Acronym Geek, 10 February 2012, <http://www.acronymgeek.com/E4> [accessed 10 February 2012] |
| Chicago | "E4", http://www.acronymgeek.com/E4 (accessed February 10, 2012). |
| CBE/CSE | E4 [Internet]. Acronym Geek; 2012 Feb 10 [cited 2012 Feb 10]. Available from: http://www.acronymgeek.com/E4. |
| Bluebook | E4, http://www.acronymgeek.com/E4 (last visited February 10, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, E4, http://www.acronymgeek.com/E4 (optional description here) (as of Feb. 10, 2012, 09:39). |
| AMA | E4. Acronym Geek. February 10, 2012, 09:39. Available at: http://www.acronymgeek.com/E4. Accessed February 10, 2012, 09:39. |