Lara F. Horani and  Shurong Tong,  Rating the Importance of Customer Requirements for Green Product Using Analytic Hierarchy Process Methodology.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2018, vol. 136(4). 557 - 563
    [viewed 12 July 2020]. Available from: https://publications.waset.org/pdf/10009004.