M. Ravindra and  R. Srinivasa Rao,  Dynamic State Estimation with Optimal PMU and Conventional Measurements for Complete Observability.   journal   = {International Journal of Energy and Power Engineering}, [online]. World Academy of Science, Engineering and Technology.
    May 2017, vol. 124(4). 448 - 456
    [viewed 18 April 2021]. Available from: https://publications.waset.org/pdf/10007307.