https://www.mastermindtoys.com/91-Authentic-Wooden-Yo-Yo-Pro.aspx
https://www.yoyoplay.com/duncan-retro-wooden-butterfly-yoyo/
http://creekbed.org/collection/yoyo.htm
http://theharlow.net/cut-the-ribbon-pedro-flores/
http://ucifilam.blogspot.com/2009/11/inventor-of-flores-yo-yo-philippine.html
https://www.flickr.com/photos/97651231@N00/10106820623
https://en.wikipedia.org/wiki/Pedro_Flores_(inventor)
https://pxhere.com/en/photo/1443299
https://en.wikipedia.org/wiki/Yo-yo
https://www.brooklynmuseum.org/opencollection/labs/splitsecond/painting?id=78
https://www.pinterest.com/pin/189854940519996523/
http://discoveringmandarin.blogspot.com/2009/08/chinese-yo-yo-diabolo.html
http://www.ancientpages.com/2019/05/13/oldest-yo-yo-dates-back-to-400-500-b-c/
http://pscelebrityhomes.com/celebrity-index-d-f/donald-duncan-movie-colony/
https://www.youtube.com/watch?v=2ZkR_nDrBm0
https://www.youtube.com/watch?v=iU8DkyHKz6I