1. 1. J. Mitola, “Cognitive radio: An integrated agent architecture for software defined radio,” Ph. D. dissertation, Royal Inst. Technol. (KTH), Stockholm, Sweden, Dec. 2000.
   2. J. Lee, H. Wang, J. G. Andrews, and D. Hong, “Outage probability of cognitive relay networks with interference constraints,” IEEE Trans. Wireless Commun., vol. 10, no. 2, pp. 390-395, Feb. 2011.
   3. Y. Deng, M. Elkashlan, N. Yang, P. L. Yeoh, and R. K. Mallik, “Impact of primary network on secondary network with generalized selection combining,” IEEE Trans. Veh. Technol., vol. 64, no. 7, pp. 3280-3285, Jul. 2015.
   4. B. Zhong, Z. Zhang, X. Zhang, J. Wang, and K. Long, “Partial relay selection with fixed-gain relays and outdated CSI in underlay cognitive networks”, IEEE Trans. Veh. Technol., vol. 62, no. 9, pp. 4696-4701, Nov. 2013.
   5. Y. Huang, F. S. Al-Qahtani, C. Zhong, Q. Wu, J. Wang, and H. M. Alnuweiri, “Cognitive MIMO relaying networks with primary user’s interference and outdated channel state information,” IEEE Trans. Commun., vol. 62, no. 12, pp. 4241-4254, Dec. 2014
   6. H. M. Wang, F. Liu, and M. Yang.“Joint cooperative beamforming, jamming and power allocation to secure AF relay systems”, IEEE Trans. Veh. Technol., vol. 64, no. 10, pp. 4893-4898, Oct. 2015.
   7. L. J. Rodriguez, N. H. Tran, T. Q. Duong, T. Le-Ngoc, M. Elkashlan, and S. Shetty, “Physical layer security in wireless cooperative relay networks: state of the art and beyond,” IEEE Commun. Mag., vol. 53, no. 12, pp. 32-39, Mar. 2015.
   8. A. D. Wyner, “The wire-tap channel,” Bell Syst. Tech. J., vol. 54, no. 8, pp.1355-1367, Oct. 1975.
   9. Y. Zou, B. Champagne, W.-P.Zhu, and L. Hanzo, “Relay-selection improves the security-reliability trade-off in cognitive radio Systems,” IEEE Trans. Commun., vol. 63, no. 1, pp. 215-228, Jan. 2015.