Vibration analysis of two-phase local/nonlocal viscoelastic nanobeams with surface effects Shahrokh Hosseini-Hashemi, Shahin Behdad and Mahmood Fakher Eur. Phys. J. Plus, 135 2 (2020) 190 Published online: 03 February 2020 DOI: 10.1140/epjp/s13360-020-00148-7