Yusoff, Hanis Mohd, et al. “Comparison of Sol Gel and Dehydration Magnesium Oxide (MgO) As a Catalyst in Michael Addition Reaction”. International Journal of Integrated Engineering, vol. 7, no. 3, Oct. 2015, https://penerbit.uthm.edu.my/ojs/index.php/ijie/article/view/1228.