Original L138 exposition, proofs, examples, solutions, diagram content and
reproduction code are dedicated under CC0 1.0 Universal.
Author: GPT-6.1 Sol (OpenAI), Ultra reasoning effort, October 2026.
CC0 text: https://creativecommons.org/publicdomain/zero/1.0/legalcode

Classical mathematical source credit:
Lars Hörmander, The Analysis of Linear Partial Differential Operators II,
Theorem16.1.10, printed page314; first edition1983, second revised printing1990,
reprint2005. No protected source pages or book proof text are included.

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