| APA | CEI. (2012, February 14). In Acronym Geek. Retrieved 06:40, February 14, 2012, from http://www.acronymgeek.com/CEI |
| MLA | "CEI." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/CEI>. |
| MHRA | 'CEI', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/CEI> [accessed 14 February 2012] |
| Chicago | "CEI", http://www.acronymgeek.com/CEI (accessed February 14, 2012). |
| CBE/CSE | CEI [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/CEI. |
| Bluebook | CEI, http://www.acronymgeek.com/CEI (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, CEI, http://www.acronymgeek.com/CEI (optional description here) (as of Feb. 14, 2012, 06:40). |
| AMA | CEI. Acronym Geek. February 14, 2012, 06:40. Available at: http://www.acronymgeek.com/CEI. Accessed February 14, 2012, 06:40. |