Nguyen, Sang-Quang, and Chi-Bao Le. “Physical Layer Security for Keyhole-Based NOMA Downlink Systems With a Multi-Antenna Eavesdropper”. Journal of Telecommunications and Information Technology, vol. 101, no. 3, July 2025, pp. 16-22, https://doi.org/10.26636/jtit.2025.3.2116.