docs: "References" page added

docs/appendix/references.md

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+# References
+
+[`ISO80000`](#ISO80000){ #ISO80000 }
+
+:   [ISO 80000-1:2009(E) "Quantities and units — Part 1: General"](https://www.iso.org/standard/30669.html),
+    International Organization for Standardization.
+
+[`SIBrochure`](#SIBrochure){ #SIBrochure }
+
+:   [The International System of Units (SI)](https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf),
+    International Bureau of Weights and Measures (20 May 2019), ISBN 978-92-822-2272-0.
+
+[`Quincey`](#Quincey){ #Quincey }
+:   ["Angles in the SI: a detailed proposal for solving the problem](https://arxiv.org/pdf/2108.05704.pdf),
+    Quincey, Paul (1 October 2021).