TY - JOUR AU - Aleksandar Obradović AU - Slaviša Šalinić AU - Aleksandar Tomović TI - Free vibrations of planar serial frame structures in the case of axially functionally graded materials JO - Theoretical and applied mechanics PY - 2020 SP - 221 VL - 47 IS - 2 UR - http://geodesic.mathdoc.fr/articles/10.2298/TAM201006017O/ DO - 10.2298/TAM201006017O LA - en ID - 10_2298_TAM201006017O ER -