Kaihong Zhao and  Jiuqing Liu,  Multiple Positive Periodic Solutions of a Delayed Predatory-Prey System with Holling Type II Functional Response.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    September 2013, vol. 75(3). 440 - 444
    [viewed 26 February 2020]. Available from: https://publications.waset.org/pdf/16989.