WASET
    Gholam Reza Koochaki,  Free Vibration Analysis of Functionally Graded Beams.   journal   = {International Journal of Mechanical and Mechatronics Engineering}, [online]. World Academy of Science, Engineering and Technology.
    February 2011, vol. 50(2). 514 - 517
    [viewed 23 April 2024]. Available from: https://publications.waset.org/pdf/1975.