lib/texinputs/isabellesym.sty

 \newcommand{\isasymrightleftharpoons}{\isamath{\rightleftharpoons}}
 \newcommand{\isasymdownharpoonleft}{\isamath{\downharpoonleft}}  %requires amssymb
 \newcommand{\isasymdownharpoonright}{\isamath{\downharpoonright}}  %requires amssymb
 \newcommand{\isasymupharpoonleft}{\isamath{\upharpoonleft}}  %requires amssymb
 \newcommand{\isasymupharpoonright}{\isamath{\upharpoonright}}  %requires amssymb
+\newcommand{\isasymrestriction}{\isamath{\restriction}}  %requires amssymb
 \newcommand{\isasymleadsto}{\isamath{\leadsto}}  %requires amssymb
 \newcommand{\isasymup}{\isamath{\uparrow}}
 \newcommand{\isasymUp}{\isamath{\Uparrow}}
 \newcommand{\isasymdown}{\isamath{\downarrow}}
 \newcommand{\isasymDown}{\isamath{\Downarrow}}