Strongly Nonlinear Differential Equations with Carlitz Derivatives over   a Function Field
  In earlier papers the author studied some classes of equations with Carlitz derivatives for $\mathbb F_q$-linear functions, which are the natural function field counterparts of linear ordinary differential equations. Here we consider equations containing self-compositions $u\circ u\circ ... \circ u$ of the unknown function. As an algebraic background, imbeddings of the composition ring of $\mathbb F_q$-linear holomorphic functions into skew fields are considered. 
Anatoly N. Kochubei