Ich, Le Cong, et al. “Free Vibration of Bidirectional Functionally Graded Sandwich Beams Partially Resting on Pasternak Foundation Based on a Sinusoidal Theory”. Vietnam Journal of Science and Technology, vol. 58, no. 5, Oct. 2020, pp. 635-49, doi:10.15625/2525-2518/58/5/15052.