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On $$C^2$$ solutions of a functional equations. (Chinese. English summary) Zbl 1015.39007
Summary: Concerning iterative equations higher smoothness is a difficult problem. As an exploration in this paper the $$C^2$$ smoothness of solutions of an iterative functional equation, more general than polynomial-like ones, is discussed.

##### MSC:
 39B12 Iteration theory, iterative and composite equations 39B22 Functional equations for real functions 37E05 Dynamical systems involving maps of the interval (piecewise continuous, continuous, smooth)