Mesbaholdin Salami and  Farzad Movahedi Sobhani and  Mohammad Sadegh Ghazizadeh,  Multistage Data Envelopment Analysis Model for Malmquist Productivity Index Using Grey's System Theory to Evaluate Performance of Electric Power Supply Chain in Iran.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    August 2019, vol. 153(9). 1181 - 1192
    [viewed 19 November 2019]. Available from: https://publications.waset.org/pdf/10010717.