Lakkam, Supachai, and Polrut Boonmee. 2020. “A study of bending stress of thickening wall materials and energy absorption of square bar materials derived from natural materials”. UTK RESEARCH JOURNAL 14 (1). Bankok, Thailand:40-51. https://ph02.tci-thaijo.org/index.php/rmutk/article/view/221206.