Donglan Zha and  Ning Ding,  Research on Regional Energy Saving Potential Based on Nonparametric Radial Adjustment and Slack Adjustment.   journal   = {International Journal of Environmental and Ecological Engineering}, [online]. World Academy of Science, Engineering and Technology.
    August 2012, vol. 68(8). 485 - 491
    [viewed 04 May 2024]. Available from: https://publications.waset.org/pdf/12532.