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Sur les points singuliers des équations différentielles. (French) Zbl 0252.34031

Sémin. Goulaouic-Schwartz 1971-1972, Équat. dériv. part. anal. fonct., Exp. No. XX, 13 p. (1972).
In this paper the author defines a measure of irregularity of singular points for an ordinary linear operator with holomorphic coefficients and studies its elementary properties.

MSC:

34C05 Topological structure of integral curves, singular points, limit cycles of ordinary differential equations
34A25 Analytical theory of ordinary differential equations: series, transformations, transforms, operational calculus, etc.
34A12 Initial value problems, existence, uniqueness, continuous dependence and continuation of solutions to ordinary differential equations
34G99 Differential equations in abstract spaces