F. Mohd Razali, N. A. Abdul Aziz, S. A. Salim, R. Mohamad Rasli, and N. F. Zulkefly, “The effects of free rotate gestures in multi-touch screen design on childrens’ achievement in learning shape for pre-school children”, SAECJ, vol. 6, pp. 19–26, Oct. 2017.