From the Sources Section
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^ Advanced Yo-Yo Tricks for Kids, Editors of Publications International, Ltd., howstuffworks.com
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^ Extraordinary Origins of Everyday Things by Charles Panati,Harper Paperbacks (1989) ISBN 0060964197
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^ Eloisa Gomez Borah, Was the Yo-Yo really a weapon?, retrieved 2008-03-09
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^ U.S. Patent 59,745 dated November 20, 1866
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^ Online Etymology Dictionary. Etymonline.com. Retrieved on 2012-04-09.
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^ By admin (2010-04-27). "Home of the National Yo-Yo Contest, National Yo-Yo Museum and National Yo-Yo League". National Yo-Yo. Retrieved 2011-05-23.
^ Tzeng, Grace. "Toy Story: Gravity-defying yo-yo tricks on display at California State Yo-Yo Championships". AsianWeek. Retrieved on 8 September 2008.
^ David Sutherland (1999). Alma and the Magic Yo-Yo. Mammoth. ISBN 978-0-7497-3780-1.
^ Yo-Yo Basics, howstuffworks.com.
^ American Yo-Yo Association website.
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^ Team Offstring Superheroes, October 17, 2008.
^ Lucky's Collectors Guide to 20th Century Yo-Yos, 1999
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^ www.YoYoSkills.com/hans-interview.html - Interview with Hans Van Dan Elzen, YoYoFactory
^ U.S. Patent 5,813,897 Filed May 8, 1997; Issued September 29, 1998
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^ "Interview with Hans Van Dan Elzen, YoYoFactory President". Yoyoskills.com. 2008-12-06. Retrieved 2011-05-23.
^ U.S. Patent 6,331,132 Filed July 27, 1999; Issued December 18, 2001
^ U.S. Patent 7,192,330 Filed October 29, 1999; Issued December 19, 2000