Fontanarosa, Phil B., and Stacy Christiansen. "Products and Quotients of Unit Symbols." AMA Manual of Style. 20090401. Oxford University Press. Date of access 21 May. 2013, <http://www.amamanualofstyle.com/view/10.1093/jama/9780195176339.001.0001/med-9780195176339-div2-475>.
Fontanarosa, P., & Christiansen, S. (20090401). Products and Quotients of Unit Symbols. AMA Manual of Style. Retrieved 21 May. 2013, from http://www.amamanualofstyle.com/view/10.1093/jama/9780195176339.001.0001/med-9780195176339-div2-475.
Fontanarosa, Phil B., and Stacy Christiansen. "Products and Quotients of Unit Symbols." AMA Manual of Style. 21 May. 2013. http://www.amamanualofstyle.com/view/10.1093/jama/9780195176339.001.0001/med-9780195176339-div2-475.
Fontanarosa PB, Christiansen S. Products and quotients of unit symbols. In: AMA Manual of Style Committee. AMA Manual of Style: A Guide for Authors and Editors. 10th ed. New York, NY: Oxford University Press; 2007. http://www.amamanualofstyle.com/view/10.1093/jama/9780195176339.001.0001/med-9780195176339-div2-475. Accessed May 21, 2013.