Alexander Denzler and  Marcel Wehrle and  Andreas Meier,  Building a Hierarchical, Granular Knowledge Cube.   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    July 2015, vol. 102(6). 334 - 340
    [viewed 21 September 2020]. Available from: https://publications.waset.org/pdf/10001978.