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$X \overset{\text\small\textrm{iid}}{\sim} N(0,1^2)$

$X \overset{iid}{\sim} N(0,1^2)$

\begin{align*}
&X \overset{\text\small\rm{iid}}{\sim} N(\mu ,\sigma^2)\\
&X \overset{iid}{\sim} N(0,1^2)
\end{align*}

\end{document}
