Jean Della Dora, Evelyne Tournier. Formal solutions of differential equations in the neighborhood of singular points (Regular and Irregular). In Paul S. Wang, editor, SYMSAC 1981, Proceedings of the Symposium on Symbolic and Algebraic Manipulation, Snowbird, Utah, USA, August 5-7, 1981. pages 25-29, ACM, 1981. [doi]
Abstract is missing.