Yanfeng Chu and  Ruizhen Zhang,  Researching on the Grey Incidence among the Macroscopic Agents in the Logistics Industry System.   journal   = {International Journal of Information and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2011, vol. 59(11). 2144 - 2147
    [viewed 16 April 2021]. Available from: https://publications.waset.org/pdf/11842.