Makchay, Panchanok, Somjai Kajorncheappunngam, and Kanyarat Holasut. 2014. “Property of polylactic acid synthesized from 85% lactic acid via direct condensation polymerization”. Engineering and Applied Science Research 40 (2):237-45. https://ph01.tci-thaijo.org/index.php/easr/article/view/19104.