Achim Washington and  Reece Clothier and  Jose Silva,  Managing Uncertainty in Unmanned Aircraft System Safety Performance Requirements Compliance Process.   journal   = {International Journal of Mechanical and Mechatronics Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2018, vol. 137(5). 502 - 511
    [viewed 23 October 2019]. Available from: https://publications.waset.org/pdf/10008962.