Stress-driven nonlocal and strain gradient formulations of Timoshenko nanobeams M. Faraji Oskouie, R. Ansari and H. Rouhi Eur. Phys. J. Plus, 133 8 (2018) 336 Published online: 24 August 2018 DOI: 10.1140/epjp/i2018-12183-x