Graph Neural Network-Based Beamforming Optimization for Multi-BS RIS-Aided Communication Systems. - Seo, Seung-Hwan; Choi, Seong-Gyun; Yu, Ji-Hee; Choi, Yoon-Ju; Tong, Ki-Chang; Choi, Min-Hyeok; Jung, Yeong-Gyun; Song, Hyoung-Kyu; You, Young-Hwan (Mathematics (2227-7390), 2025)