Siti Salwa Abd Gani. “Optimization of Moisturizing Clay Soap Containing Pitaya (Hylocereus Polyrhizus) Seed Extract Using D-Optimal Mixture Experimental Design”. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, vol. 43, no. 1, Mar. 2018, pp. 45-57, https://semarakilmu.com.my/journals/index.php/fluid_mechanics_thermal_sciences/article/view/2662.