Zero-Curvature Representation and Dual Formulations of $N=2$   Supersymmetric Gauge Theory in Harmonic Superspace
  Analytical harmonic superfields are the basic variables of a standard harmonic formalism of SYM^2_4-theory. We consider superfield actions for alternative formulations of this theory using the unconstrained harmonic prepotentials. The corresponding equations of motion are equivalent to the component field equations of SYM^2_4-theory. The analyticity condition appears only on-shell as the zero-curvature equation in the alternative formulations. 
B.M.Zupnik