Rough timeline of bowling ball coverstocks. Information derived from sources:
<ul><li>Carrubba, Rich. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180917215354/https://www.bowlingball.com/BowlVersity/bowling-ball-evolution">Bowling Ball Evolution</a>. <i>BowlingBall.com </i>(Bowlversity educational section)'<b> (June 2012). Archived from <a rel="nofollow" class="external text" href="https://www.bowlingball.com/BowlVersity/bowling-ball-evolution">the original</a> on <span class="mw-formatted-date" title="2018-09-17">September 17, 2018</span>.</b></li></ul><ul><li>Siefers, Nick. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180920011257/https://www.bowlingdigital.com/bowl/node/2324">Understanding the relationship between core and cover stock</a>. <i>BowlingDigital.com </i>(Courtesy of USBC Equipment Specification and Certification)'<b> (<span class="mw-formatted-date" title="2007-04-23">April 23, 2007</span>). Archived from <a rel="nofollow" class="external text" href="https://www.bowlingdigital.com/bowl/node/2324">the original</a> on <span class="mw-formatted-date" title="2018-09-20">September 20, 2018</span>.</b></li></ul>
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