"Uruguay River." The Columbia Electronic Encyclopedia, Sixth Edition. Columbia University Press., 2011. Answers.com 17 Nov. 2011. http://www.answers.com/topic/uruguay-river
"Uruguay River." The American Heritage® Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. Answers.com 17 Nov. 2011. http://www.answers.com/topic/uruguay-river