HENRY, J., K. MOHANRAJ, S. KANNAN, S. BARATHAN, and G. SIVAKUMAR. “Effect of Butanol and Propylene Glycol in Amorphous MnO2 Nanoparticles”. Walailak Journal of Science and Technology (WJST), vol. 11, no. 5, Dec. 2013, pp. 437-43, https://wjst.wu.ac.th/index.php/wjst/article/view/590.