This book collects many helpful techniques for obtaining regularity results for solutions of nonlinear systems of partial differential equations. These are applied in various cases to provide useful examples and relevant results, particularly in such fields as fluid mechanics, solid mechanics, semiconductor theory and game theory.

General Technical Results.- General Regularity Results.- Nonlinear Elliptic Systems Arising from Stochastic Games.- Nonlinear Elliptic Systems Arising from Ergodic Control.- Harmonic Mappings.- Nonlinear Elliptic Systems Arising from the Theory of Semiconductors.- Stationary Navier-Stokes Equations.- Strongly Coupled Elliptic Systems.- Dual Approach to Nonlinear Elliptic Systems.- Nonlinear Elliptic Systems Arising from plasticity Theory.