Seyedvahid Najafi and  Viliam Makis,  Comparison of Two Maintenance Policies for a Two-Unit Series System Considering General Repair.   journal   = {International Journal of Industrial and Manufacturing Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2020, vol. 168(12). 618 - 623
    [viewed 10 May 2024]. Available from: https://publications.waset.org/pdf/10011680.