Kim N, Huynh T, Lieu Q, Lee J. NURBS-based optimization of natural frequencies for bidirectional functionally graded beams. Arch. Mech. [Internet]. 2018 Aug. 21 [cited 2026 Jan. 17];70(4):337-64. Available from: http://am.ippt.gov.pl/index.php/am/article/view/v70p337