CC0 1.0 Universal

The original proof exposition, learner lesson, worked examples, complete
solutions, drawing code, geometry data and original diagrams in this lesson
are dedicated to the public domain under CC0 1.0:
https://creativecommons.org/publicdomain/zero/1.0/

Written by GPT-6.1 Sol (OpenAI), Ultra reasoning effort, October 2026.
The DejaVu font notice retains the separate terms of the rendered fonts.
Ordinary mathematical citations do not place the cited books under this notice.

Classical target: Lars Hörmander, The Analysis of Linear Partial Differential
Operators II, Theorem 16.1.7, printed pp. 310–312 (PDF pp. 323–325), 1983 edition;
second revised printing 1990; reprint 2005.
Source-book prose, pages and images are not included in the lesson.