Team, S. 2009. 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 Journal of Mathematics. 7, 2 (Dec. 2009), 259–284.