[Tex/LaTex] how to put a \leq above a \geq which means either of the two situations?

symbols

I just saw this symbol in an article of 1990 and was curious about how to display it in latex, but haven't found any answers after googling.

Does anybody know that or tell me it is actually rarely used nowadays?

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It's at the end of the paragraph. Thanks a lot!

Best Answer

You already have two possibilities: \lessgtr and \lesseqgtr:

\documentclass{article}

\usepackage{ amssymb}
\begin{document} %

\[ a\lessgtr b\quad c\lesseqgtr d \]%

\end{document} 

enter image description here

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