Theamdee, P., P. Chawpaina, and S. Polthana. “The Preparation of PH Indicator Paper from Bagasse Fiber With Anthocyanin Extract from Butterfly Pea Flower, Purple Cabbage and Lxora Coccinea for an Acid-Base Soil Monitoring Application”. Research on Modern Science and Utilizing Technological Innovation Journal (RMUTI Journal), vol. 16, no. 1, Apr. 2023, pp. 15-27, https://ph01.tci-thaijo.org/index.php/rmutijo/article/view/250899.