# Text over/under implies arrow?

I'm currently trying to write over/under an implies arrow in LaTeX (in math mode):

\implies_{text}


This places the text lower, but next to the arrow, not below it. How can I get it below the arrow?

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Related question: tex.stackexchange.com/questions/4813/extendible-equals-sign if you're willing to load amsmath then I strongly expect that the answer to your question will be very similar to the accepted answer to that question. –  Andrew Stacey Nov 9 '10 at 19:21
Already running amsmath, sorry. –  Femaref Nov 9 '10 at 19:25
That you are already running amsmath is a good thing, not a bad one! –  Andrew Stacey Nov 9 '10 at 19:45
the "sorry" wasn't for running amsmath, but not providing the detail in the question ;) –  Femaref Nov 9 '10 at 20:04

You can use \xRightarrow[below]{above} from the mathtools (or extpfeil) package or \xLongrightarrow[below]{above} from extarrows. (Have a look at “How to look up a math symbol?” for ideas how you can easily find a particular symbol.)
If you want to keep the the same arrow length as implies, you can use \underset and \overset from amsmath, e.g. \underset{below}{\implies}, or maybe \underset{\mathclap{below}}{\implies} (\mathclap makes it so that “below” doesn’t introduce extra vertical space if it is longer than the arrow. It is included in the immensely useful mathtools package).
\underset FTW. And I need to learn more about mathtools. –  Matthew Leingang Nov 9 '10 at 19:56