R. Leelaruji and  V. Knazkins,  The Use of Voltage Stability Indices and Proposed Instability Prediction to Coordinate with Protection Systems.   journal   = {International Journal of Electrical and Computer Engineering}, [online]. World Academy of Science, Engineering and Technology.
    May 2009, vol. 29(5). 1146 - 1151
    [viewed 22 September 2020]. Available from: https://publications.waset.org/pdf/3856.