Mohd Ariff, Muhammad Shafiq Najemee, et al. “A Comparison Study of Radioactivity and Radiation Hazard Index Between Legal and Illegal Cigarettes”. International Journal of Integrated Engineering, vol. 10, no. 7, Nov. 2018, https://penerbit.uthm.edu.my/ojs/index.php/ijie/article/view/3474.