On preparation theorems for R_{an, exp}-definable functions

In this article we give strong versions for preparation theorems for $\mathbb{R}_{\textnormal{an,exp}}$-definable functions outgoing from methods of Lion and Rolin ($\mathbb{R}_{\textnormal{an,exp}}$ is the o-minimal structure generated by all restricted analytic functions and the global exponential function). By a deep model theoretic fact of Van den Dries, Macintyre and Marker every $\mathbb{R}_{\textnormal{an,exp}}$-definable function is piecewise given by $\mathcal{L}_{\textnormal{an}}(\exp,\log)$-terms where $\mathcal{L}_{\textnormal{an}}(\exp,\log)$ denotes the language of ordered rings augmented by all restricted analytic functions, the global exponential and the global logarithm. So our idea is to consider log-analytic functions at first, i.e. functions which are iterated compositions from either side of globally subanalytic functions and the global logarithm, and then $\mathbb{R}_{\textnormal{an,exp}}$-definable functions as compositions of log-analytic functions and the global exponential.