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The textual narrative, diagrams, proposition layout, page structure, and accompanying images in the following directories are © David E. Joyce, used by his permission:
Dr. Joyce wrote these between 1996 and 2020 as part of his online edition of the Elements and supplementary materials, originally hosted at Clark University. His permission to republish this content on euclids-elements.org — and to port the underlying applet to TypeScript as geomlib — was granted in May 2026 to Nelson Brown.
For the exact wording of his permission grant, see the geomlib NOTICE in the library's source repository on GitHub.
Third parties wishing to redistribute Dr. Joyce's narrative content should obtain separate permission from him.
All rights are reserved with respect to the narrative content republished on this site — the textual proofs, commentary, proposition layout, and accompanying images.
Web links to this material may be freely made, either to the original at http://aleph0.clarku.edu/~djoyce/java/elements/elements.html or to this site at https://www.euclids-elements.org/.
The TypeScript library that drives all interactive diagrams on this site is open source under the MIT License, under joint copyright:
© 1996–2020 David E. Joyce, 2019–2026 Nelson Brown.
The Joyce years credit his authorship of the original Java applet and its continued maintenance through the Elements web edition. The Brown years credit the TypeScript port.
Library source: github.com/brownnrl/euclid. Published as @brownnrl/geomlib on npm. For the full attribution and permission text, see the NOTICE.