Mohamad Dzol, Muhammad Amir Aqil, et al. “Catalytic Performance of NiO Eggshell Prepared via Sol-Gel Technique in Pyrolysis of Mixed HDPE and PET”. International Journal of Integrated Engineering, vol. 18, no. 3, Apr. 2026, pp. 48-62, https://penerbit.uthm.edu.my/ojs/index.php/ijie/article/view/20747.