WASET
    Da-kuan Wei and  Xian-zhong Zhou and  Dong-jun Xin and  Zhi-wei Chen,  Variable Rough Set Model and Its Knowledge Reduction for Incomplete and Fuzzy Decision Information Systems.   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    June 2007, vol. 6(6). 1642 - 1646
    [viewed 19 April 2024]. Available from: https://publications.waset.org/pdf/10310.