# LATEX question about logical symbol

For the "entailment" relation we have $\models$ (\models or \vDash).

Sometimes I need "logical equivalence", sometimes symbolized as "=||=".

Question : where I can find $\leftmodels$ or one of its equivalent ?

How about $=\hspace{-.5em}||\hspace{-.5em}=$
$=\hspace{-.5em}||\hspace{-.5em}=$
• Why not $=\hspace{-.5em}|\models$? – Asaf Karagila Apr 14 '15 at 15:22