F. Gökgöz and  M. E. Atmaca,  Financial Portfolio Optimization in Electricity Markets: Evaluation via Sharpe Ratio.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2016, vol. 119(11). 3578 - 3586
    [viewed 18 April 2021]. Available from: https://publications.waset.org/pdf/10005674.