Vibration analysis of two-phase local/nonlocal viscoelastic nanobeams with surface effectsShahrokh Hosseini-Hashemi, Shahin Behdad and Mahmood FakherEur. Phys. J. Plus, 135 2 (2020) 190DOI: https://doi.org/10.1140/epjp/s13360-020-00148-7