M. L. Firdaus, S. Yuliafitri, E. Swistoro, G. Ghufira, and R. W. Wardana, “Implementation of discovery learning on electromagnetic wave material based on adsorption Congo Red by silica from Bengkulu beach sand”, J. Sc. Edu. Research, vol. 3, no. 2, pp. 103–107, Nov. 2019.