1. Ding Sun-hong, Uniqueness of limit cycle of predator-prey system,Science Bulletin,13 (1985), 785–788. (in Chinese)
2. Hsu, S.B., S.P. Hubbell and P. Waltman, Competing predator, SIAM,J. Appl. Math.,35 (1978), 617–625.
3. Hastings, Alan, Global stability of two species systems,J. Math. Biology,5 (1978), 399–403.
4. Cheng Kuo-sheng, Uniqueness of limit cycle for a predator-prey system, SIAM,J. Math. Anal.,12, 4 (1981), 541–548.