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2018
It is built from checkable properties of the record itself: whether the article has a DOI, how many independent sources confirmed its data, whether the required fields are filled in, and how recent the latest confirmation is. Disagreement between sources and a missing identifier lower it. A value of 80 or above means the record was published without further checking; 60 to 79 means it is published at reduced confidence, with a manual check advisable. A record verified by an editor by hand is never pushed below 90 by a recalculation. This scores our data about the article, not the article itself.
In this paper, for the Sturm–Liouville operator with a parameter that changes sign the following results: (1) the existence of the resolvent, (2) the criterion of the spectrum discreteness, (3) two-sided estimates of approximation numbers (s-numbers) are obtained. These results are applied to the study of the spectral properties of differential operators of elliptic, parabolic and hyperbolic types.