Esra E. Aleisa and  Li Lin,  Abstraction Hierarchies for Engineering Design.   journal   = {International Journal of Industrial and Manufacturing Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2008, vol. 21(9). 1075 - 1087
    [viewed 26 April 2024]. Available from: https://publications.waset.org/pdf/3573.