WASET
    Alexandr A. Penin,  The Invariant Properties of Two-Port Circuits.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2009, vol. 28(4). 878 - 884
    [viewed 09 May 2024]. Available from: https://publications.waset.org/pdf/5517.