Effective Action of N=2 Supersymmetric Field Theories in Harmonic   Superspace Approach
  The paper is a brief review of the works devoted to problem of effective action in N=2 super Yang-Mills theories in harmonic superspace approach. The formulation of N=2 superfield models in harmonic superspace is discussed, background field method for N=2 super Yang-Mills theory is constructed and general structure of effective action in harmonic superspace is investigated. It is shown how the holomorphic and non-holomorphic contributions to effective action can be calculated within the harmonic superspace approach. 
I.L. Buchbinder (Tomsk State Pedagogical University)