Canjie Chen, and Quanyuan Feng. “A Compact Broadband Circularly Polarized Slot Antenna for Universal UHF RFID Reader and GPS”. The Applied Computational Electromagnetics Society Journal (ACES), vol. 36, no. 05, July 2021, pp. 589-95, https://journals.riverpublishers.com/index.php/ACES/article/view/8821.