# How to put something at the top of the \longrightarrow?

I would like to put something at the top of the \longrightarrow, something like \longrightarrow^{k\rightarrow\infty}. However, instead of putting k\rightarrow\infty on the top right corner, I would like to put it in the middle on the top of \longrightarrow. Could someone help me?

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In this instance, I think \xrightarrow would suit you better. Here's an example using the former, and the traditional \overset from amsmath:

\documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}
$\mathcal{X}\overset{k\rightarrow\infty}{\longrightarrow}\mathcal{Y} \qquad \mathcal{X}\xrightarrow{k\rightarrow\infty}\mathcal{Y}$
\end{document}


\xrightarrow{<stuff>} is an extensible arrow, which conforms in length to the overset argument <stuff>.

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Thanks a lot! That's exactly what I wanted! –  Paul Feb 27 '12 at 6:45

Use

\stackrel{k\rightarrow\infty}{\longrightarrow}


Alternatively, if you want the long arrow to stretch you may prefer

\xrightarrow{k\rightarrow\infty}


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Thank you for your answer. However, I can accept only one answer. Anyway, thank you! –  Paul Feb 27 '12 at 6:46