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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.

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
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