This entry is about Pierre Deligne’s article
The main theorem is a Tannakian reconstruction theorem, which repairs a problem in the book
which had a substantial gap in the proof of the main theorem.
At the end of the article there is an application to the differential Galois theory (which has been earlier much studied by A. R. Magid) which is the Galois theory for differential rather than algebraic equations.
A followup is