WASET
    Shiping Wang and  Peiyong Zhu and  William Zhu,  Structure of Covering-based Rough Sets.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    January 2010, vol. 37(1). 193 - 196
    [viewed 09 May 2024]. Available from: https://publications.waset.org/pdf/13163.