Square version of \subsetneq

Question

Does anyone know how to make a 'square version' of \subsetneq? I tried \sqsubsetneq, but it doesn't work.

Thanks! Joon

Answer 1

You need the mathabx package:

For such things I highly recommend trying: texdoc symbols

Code:

\documentclass[border=5mm]{standalone}
\usepackage{mathabx}
\begin{document}

  $X \sqsubsetneq B$

\end{document}

Edit: just to complete, here is a print screen from the documentation cited.