Closure to "Critical shear stress for erosion of sand and mud mixtures" by WEIMING WU, CHAMIL PERERA, JARRELL SMITH and ALEJANDRO SANCHEZ, J. Hydraulic Res. 56(1), 2018, 96–110. Issue 3 (15th April 2020) - Wu, Weiming; Perera, Chamil; Smith, Jarrell; Sanchez, Alejandro