diff --git a/Geometric-algebra.md b/Geometric-algebra.md
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--- a/Geometric-algebra.md
+++ b/Geometric-algebra.md
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-[ganja.js](https://enkimute.github.io/ganja.js/) – Tons of examples! Also has a [Julia interface](https://github.com/chakravala/Ganja.jl).
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+[ganja.js](https://enkimute.github.io/ganja.js/) – Tons of examples! Also has a [Julia interface](https://github.com/chakravala/Ganja.jl).
+- The $G_{6,3}$ Clifford algebra extends $G_{4,1}$ to encode all quadric surfaces. [This paper](https://doi.org/10.1007/s00006-014-0442-8) has details.
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