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Notation: $L/K$, finite extension of global fields $K^\times$, unit group of $K$ $L^\times$, units group of $L$ $\mathbb{A}_L^\times$, ideles of $L$ $N_{L/K}$, the norm map The knot group of an ...

The German Wikipedia entry for Ernst Witt https://de.wikipedia.org/wiki/Ernst_Witt has a photo of his grave in Hamburg. The bottom part has a visible text "Artin Brueche" (Artin fractions) but the ...