src/HOL/Probability/document/root.tex

--- a/src/HOL/Probability/document/root.tex	Mon Dec 15 07:20:49 2014 +0100
+++ b/src/HOL/Probability/document/root.tex	Wed Dec 17 16:10:30 2014 +0100
@@ -3,6 +3,7 @@
 
 \documentclass[11pt,a4paper]{article}
 \usepackage{graphicx,isabelle,isabellesym,latexsym,textcomp}
+\usepackage{amssymb}
 \usepackage[only,bigsqcap]{stmaryrd}
 \usepackage[utf8]{inputenc}
 \usepackage{pdfsetup}