Erika Martinez Ramirez and  Rene V. Mayorga,  A Rough Sets Approach for Relevant Internet/Web Online Searching.   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2009, vol. 33(9). 2262 - 2271
    [viewed 23 April 2021]. Available from: https://publications.waset.org/pdf/14609.