Ishak, N. S. ., M. H. . Dahri, N. .A. . Awang, W. Y. . Chong, and F. C. . Seman. “Realization of Circular Slot Frequency Selective Surfaces Using Photoplotter and Wet Etching Technique for Terahertz Material Sensing Applications”. International Journal of Integrated Engineering, vol. 12, no. 6, May 2020, pp. 49-54, https://publisher.uthm.edu.my/ojs/index.php/ijie/article/view/6287.