## What’s the motivation of Lagrangian distribution and its application?

Hormander asserts that Lagrangian distribution(LD) is a generation of conormal distribution(CD), which is useful in boundary value problems. CD discribes something tagential to a closed submanifold of base space, and LD to a Lagrangian submanifold of vector bundle over base space. So, what's the application of this concept or tools?

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