Bhaskar, Manju, and Thomaskutty Mathew. “Ultra-Wideband Bandpass Filter With Notch Band Based on Quadratic Koch Island Structure”. Indonesian Journal of Electrical Engineering and Informatics (IJEEI), vol. 9, no. 3, Sept. 2021, pp. 793-8, https://doi.org/10.52549/ijeei.v9i3.2547.