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3. Calendering, n.d. http://polymer360.blogspot.com/2017/06/calendering_6.html (July 2020).
4. Coextrusion Example, n.d. http://www.flemingptc.co.uk/research/ (July 2020).
5. Die Swell, n.d. https://www.azom.com/article.aspx?ArticleID=13578 (July 2020).