Amir Abbas Najafi and  Nima Zoraghi and  Fatemeh Azimi,  Scheduling a Project to Minimize Costs of Material Requirements.   journal   = {International Journal of Industrial and Manufacturing Engineering}, [online]. World Academy of Science, Engineering and Technology.
    June 2011, vol. 54(6). 968 - 971
    [viewed 24 January 2020]. Available from: https://publications.waset.org/pdf/9664.