Irshad Ullah, Muhammad Irfan Khattak, and Muhammad Farooq. “Designing and Analyzing a Planer Butler Matrix for Phased Array Antenna for Future 5G Applications”. IEEEP New Horizons Journal, vol. 101, no. 1, Dec. 2019, pp. 39-45, https://ieeepnhrj.org/index.php/ieeep/article/view/18.