Serkan Narlı and  Ahmet Z. Ozcelik,  On Generalizing Rough Set Theory via using a Filter.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    July 2008, vol. 19(7). 495 - 498
    [viewed 25 April 2024]. Available from: https://publications.waset.org/pdf/11125.