Shuffle and Fa\`a di Bruno Hopf Algebras in the Center Problem for   Ordinary Differential Equations
  In this paper we describe the Hopf algebra approach to the center problem for the differential equation $\frac{dv}{dx}=\sum_{i=1}^{\infty}a_{i}(x)v^{i+1}$, $x\in [0,T]$, and study some combinatorial properties of the first return map of this equation. The paper summarizes and extends previously developed approaches to the center problem due to Devlin and the author. 
Alexander Brudnyi
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