Mutalib, M. A., Z. Zakaria, and N. A. Shairi. “High Selectivity Microstrip Bandpass Filter Integrate With Ring Resonator Bandstop Filter”. Journal of Telecommunication, Electronic and Computer Engineering (JTEC), vol. 9, no. 2-13, Sept. 2017, pp. 39-42, https://jtec.utem.edu.my/jtec/article/view/2563.