Dariusz Dymek and  Leszek Kotulski,  Evaluation of Risk Attributes Driven by Periodically Changing System Functionality.   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2008, vol. 23(11). 3907 - 3912
    [viewed 23 January 2020]. Available from: https://publications.waset.org/pdf/13407.