Ab Wahab, N., N. M. Hidayat, Z. Ismail Khan, Z. Mat Yasin, N. A. Salim, N. Othman, and M. K. M. Salleh. “Two Parallel-Coupled Rings for Narrow Bandpass Filter Application”. Journal of Telecommunication, Electronic and Computer Engineering (JTEC), vol. 8, no. 3, June 2016, pp. 73-77, https://jtec.utem.edu.my/jtec/article/view/1005.