Hung, T. Q., T. M. Tu, and D. M. Duc. “Free Vibration of Piezoelectric FGM Sandwich Beam With Porous Core Embedded in Thermal Environment and Elastic Foundation”. Journal of Science and Technology in Civil Engineering (JSTCE) - HUCE, Vol. 15, no. 4, Oct. 2021, pp. 15-28, doi:10.31814/stce.huce(nuce)2021-15(4)-02.