| APA | E4S. (2012, February 13). In Acronym Geek. Retrieved 23:44, February 13, 2012, from http://www.acronymgeek.com/E4S |
| MLA | "E4S." Acronym Geek. (2012). Acronym Geek. 13 Feb 2012 <http://www.acronymgeek.com/E4S>. |
| MHRA | 'E4S', Acronym Geek, 13 February 2012, <http://www.acronymgeek.com/E4S> [accessed 13 February 2012] |
| Chicago | "E4S", http://www.acronymgeek.com/E4S (accessed February 13, 2012). |
| CBE/CSE | E4S [Internet]. Acronym Geek; 2012 Feb 13 [cited 2012 Feb 13]. Available from: http://www.acronymgeek.com/E4S. |
| Bluebook | E4S, http://www.acronymgeek.com/E4S (last visited February 13, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, E4S, http://www.acronymgeek.com/E4S (optional description here) (as of Feb. 13, 2012, 23:44). |
| AMA | E4S. Acronym Geek. February 13, 2012, 23:44. Available at: http://www.acronymgeek.com/E4S. Accessed February 13, 2012, 23:44. |