MHD flow of micropolar and Williamson fluids over a bi-directional stretching sheet Muhammad Ramzan, Abdullah Dawar, Anwar Saeed, Poom Kumam and Wiboonsak Watthayu Eur. Phys. J. Plus, 137 7 (2022) 869 Published online: 28 July 2022 DOI: 10.1140/epjp/s13360-022-03071-1