Ma, R. ., and Q. . Feng. “Broadband CPW-Fed Circularly Polarized Square Slot Antenna for Universal UHF RFID Handheld Reader”. The Applied Computational Electromagnetics Society Journal (ACES), vol. 36, no. 06, Nov. 2021, pp. 747-54, https://journals.riverpublishers.com/index.php/ACES/article/view/12085.