S. Team, “Exact Solutions of Steady Plane Flows of an Incompressible Fluid of Variable Viscosity in The Presence of Unknown External Force Using ($\varepsilon,\psi$ )– or ($\eta,\psi$)-Coordinates: Rana Khalid Naeem, Asif Mansoor, Waseem Ahmed Khan”, Thai J Math, vol. 7, no. 2, pp. 259–284, Dec. 2009.