PageHeader : Funkcialaj Evacioj, 22 (1979) 197-221 Title : A General Theory of Invariants for Meromorphic Title : Differential Equations; AuthorInfo : Part I, Formal Invariants AuthorInfo : By AuthorInfo : W. Baiser, W. B. Jurkat* and D. A. Lutz* AuthorInfo : (Univ. Ulm, West Germany, Syracuse Univ. and Univ. Wisconsin-Milwaukee, U.S.A.) section : 0. Introduction section : 1. Structure of formal solutions section : 2. Proof of Theorem I section : 3. Formal meromorphic invariants section : 4. Formal analytic and Birkhoff invariants section : 5. The case $\mathrm{r}=0$ , a singularity of the first kind section : References