Pan Wang and  Yongkun Li,  Multiple Positive Periodic Solutions to a Predator-prey system with Harvesting Terms and Holling II Type Functional Response.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    December 2011, vol. 60(12). 1882 - 1889
    [viewed 26 April 2024]. Available from: https://publications.waset.org/pdf/11513.