| APA | E4SI. (2012, February 15). In Acronym Geek. Retrieved 11:28, February 15, 2012, from http://www.acronymgeek.com/E4SI |
| MLA | "E4SI." Acronym Geek. (2012). Acronym Geek. 15 Feb 2012 <http://www.acronymgeek.com/E4SI>. |
| MHRA | 'E4SI', Acronym Geek, 15 February 2012, <http://www.acronymgeek.com/E4SI> [accessed 15 February 2012] |
| Chicago | "E4SI", http://www.acronymgeek.com/E4SI (accessed February 15, 2012). |
| CBE/CSE | E4SI [Internet]. Acronym Geek; 2012 Feb 15 [cited 2012 Feb 15]. Available from: http://www.acronymgeek.com/E4SI. |
| Bluebook | E4SI, http://www.acronymgeek.com/E4SI (last visited February 15, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, E4SI, http://www.acronymgeek.com/E4SI (optional description here) (as of Feb. 15, 2012, 11:28). |
| AMA | E4SI. Acronym Geek. February 15, 2012, 11:28. Available at: http://www.acronymgeek.com/E4SI. Accessed February 15, 2012, 11:28. |