WASET
    Lili Sun and  Hua Wang,  A Purpose Based Usage Access Control Model.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    January 2010, vol. 37(1). 145 - 152
    [viewed 23 April 2024]. Available from: https://publications.waset.org/pdf/5510.