I. C. B. DEAR and M. R. D. FOOT. "Vis." The Oxford Companion to World War II. Oxford University Press. 2001. Encyclopedia.com. 11 Nov. 2009 <http://www.encyclopedia.com>.
I. C. B. DEAR and M. R. D. FOOT. "Vis." The Oxford Companion to World War II. Oxford University Press. 2001. Encyclopedia.com. (November 11, 2009). http://www.encyclopedia.com/doc/1O129-Vis.html
I. C. B. DEAR and M. R. D. FOOT. "Vis." The Oxford Companion to World War II. Oxford University Press. 2001. Retrieved November 11, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O129-Vis.html