Numerical study of unsteady MHD flow of Williamson nanofluid in a permeable channel with heat source/sink and thermal radiationM. Hamid, M. Usman, Z. H. Khan, R. U. Haq and W. WangEur. Phys. J. Plus, 133 12 (2018) 527DOI: https://doi.org/10.1140/epjp/i2018-12322-5