Haluk Eren and  Ümit Çelik,  Risk Assessment for Aerial Package Delivery.   journal   = {International Journal of Electrical and Computer Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2017, vol. 130(10). 1074 - 1077
    [viewed 23 October 2019]. Available from: https://publications.waset.org/pdf/10008420.