M. Karami Khorramabadi and  A. R. Nezamabadi,  Stability of Functionally Graded Beams with Piezoelectric Layers Based on the First Order Shear Deformation Theory.   journal   = {International Journal of Electrical and Computer Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2010, vol. 47(11). 1641 - 1644
    [viewed 20 February 2020]. Available from: https://publications.waset.org/pdf/3335.