Li, Wai-Kee, Gong-Du Zhou, and Thomas Chung Wai Mak. "Structural Chemistry of Group 17 and Group 18 Elements." Advanced Structural Inorganic Chemistry. : Oxford University Press, 2008-03-27. Oxford Scholarship Online. 2008-05-01. Date Accessed 21 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199216949.001.0001/acprof-9780199216949-chapter-17>.
Li, W., Zhou, G., & Wai Mak, T.(2008-03-27). Structural Chemistry of Group 17 and Group 18 Elements. In Advanced Structural Inorganic Chemistry. : Oxford University Press. Retrieved 21 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199216949.001.0001/acprof-9780199216949-chapter-17.
Li, Wai-Kee, Gong-Du Zhou, and Thomas Chung Wai Mak. "Structural Chemistry of Group 17 and Group 18 Elements." In Advanced Structural Inorganic Chemistry. : Oxford University Press, 2008-03-27. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199216949.001.0001/acprof-9780199216949-chapter-17.
Li W, Zhou G, Wai Mak TC. Structural Chemistry of Group 17 and Group 18 Elements. In: Li W, Zhou G, Mak T. Advanced Structural Inorganic Chemistry. Oxford University Press; 2008. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199216949.001.0001/acprof-9780199216949-chapter-17. Accessed May 21, 2013.