PageHeader : Funkcialaj Ekvacioj, 38 (1995) 443-472 Title : New Study on the Convergence of a Formal Transformation AuthorInfo : By AuthorInfo : Masahiro IWANO AuthorInfo : (Chuo University, Japan) AuthorInfo : Dedicated to Professor Masuo Hukuhara on his eighty eighth birthday section : 1. Introduction subsection : 1o. Assumptions. subsection : 2o. Review of some known works. subsection : 3o. Main theorem. section : 2. Formal transformation subsection : 1o. Assumptions. subsection : 2o. Formal transformation and simplified equations. subsection : 3o. Proof. subsection : 4o. Convergence of single power series. section : 3. Special truncated differential equations subsection : 1o. First transformation. subsection : 2o. Second transformation. subsection : 3o. New independent variable. section : 4. Stable domains and the curve $\Gamma(x_{0})$ subsection : 1o. Stable domains. subsection : 2o. The curve $\Gamma(x_{0})$ . subsection : 3o. Stability theorem. subsection : 4o. Proof of the case when x on $\Gamma^{\prime}$ . section : 5. Verification of inequality (4.18): $\mathscr{F}(\sigma)>0$ section : 6. Existence of solution subsection : 1o. Family of functions and mapping. subsection : 2o. $\mathscr{T}\{\mathscr{F}\}\subset \mathscr{F}$ . subsection : 3o. Verification of inequality (6.10-1) when $|\arg x_{\mathrm{o}}\mp\pi/2|\leq\pi/2-\Omega$ . subsection : 4o. Verification of inequalities (6.10-1) and (6.10-2) when $\pi/2-\Omega\leq$ $|\arg x_{\mathrm{o}}\mp\pi/2|\leq\pi-\epsilon_{\mathrm{o}}$ . subsection : 5o. Statement of Theorem. subsection : 6o. Determination of various constants. section : 7. Domain of holomorphy of the solutions section : References