| APA | S4D. (2012, February 14). In Acronym Geek. Retrieved 10:09, February 14, 2012, from http://www.acronymgeek.com/S4D |
| MLA | "S4D." Acronym Geek. (2012). Acronym Geek. 14 Feb 2012 <http://www.acronymgeek.com/S4D>. |
| MHRA | 'S4D', Acronym Geek, 14 February 2012, <http://www.acronymgeek.com/S4D> [accessed 14 February 2012] |
| Chicago | "S4D", http://www.acronymgeek.com/S4D (accessed February 14, 2012). |
| CBE/CSE | S4D [Internet]. Acronym Geek; 2012 Feb 14 [cited 2012 Feb 14]. Available from: http://www.acronymgeek.com/S4D. |
| Bluebook | S4D, http://www.acronymgeek.com/S4D (last visited February 14, 2012). |
| Bluebook: Harvard JOLT | See Acronym Geek, S4D, http://www.acronymgeek.com/S4D (optional description here) (as of Feb. 14, 2012, 10:09). |
| AMA | S4D. Acronym Geek. February 14, 2012, 10:09. Available at: http://www.acronymgeek.com/S4D. Accessed February 14, 2012, 10:09. |