Taghreed Abu-Salim,  A Framework to Assess the Maturity of Customer Involvement in the Service Design of Product-Service Systems.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    August 2015, vol. 104(8). 2843 - 2849
    [viewed 25 April 2024]. Available from: https://publications.waset.org/pdf/10002263.