src/HOL/Algebra/document/root.tex

 %\usepackage[english]{babel}           % for \<guillemotleft> \<guillemotright>
 \usepackage[latin1]{inputenc}         % for \<onesuperior>, \<onequarter>,
                                        %   \<twosuperior>, \<onehalf>,
                                        %   \<threesuperior>, \<threequarters>
                                        %   \<degree>
-%\usepackage[only,bigsqcap]{stmaryrd}  % for \<Sqinter>
+\usepackage[only,bigsqcap]{stmaryrd}  % for \<Sqinter>
 %\usepackage{wasysym}
 %\usepackage{eufrak}                   % for \<AA> ... \<ZZ>, \<aa> ... \<zz>
 %\usepackage{textcomp}                  % for \<zero> ... \<nine>, \<cent>
                                        %   \<currency>
 %\usepackage{marvosym}                 % for \<euro>