\end{equation}
In 1964, Hohenberg and Kohn showed the opposite and far less obvious result \cite{hohenberg64}.
-{\begin{theorem}
+\begin{theorem}[Hohenberg / Kohn]
For a nondegenerate ground state, the ground-state charge density uniquely determines the external potential in which the electrons reside.
\end{theorem}
\int n(\vec{r}) \left( V_2(\vec{r})-V_1(\vec{r}) \right) d\vec{r}
}_{=0}
\end{equation}
-is revealed, which proofs the Hohenberg Kohn theorem. \qed
+is revealed, which proofs the Hohenberg Kohn theorem.% \qed
\end{proof}