https://helicalcouplings.com/ujac100-90-8-8-helical-flexible-shaft-aluminum-coupling-u-joint.aspx
https://anglexinc.com/collections/all
https://web.archive.org/web/20090205182059/http://www.tpub.com/content/construction/14273/css/14273_181.htm
https://worldwide.espacenet.com/patent/search/family/024737432/publication/US1979768A?q=pn%3DUS1979768
https://www.youtube.com/watch?v=Myxb4JELa1Y
https://www.youtube.com/watch?v=cydmR0lX2t8
https://www.youtube.com/watch?v=o2IxfgV0imU
