--- a/src/ZF/Induct/document/root.tex Tue Jan 05 13:48:51 2016 +0100 +++ b/src/ZF/Induct/document/root.tex Tue Jan 05 14:25:12 2016 +0100 @@ -1,5 +1,6 @@ \documentclass[11pt,a4paper]{article} \usepackage{isabelle,isabellesym} +\usepackage{amssymb} \usepackage[utf8]{inputenc} \usepackage{pdfsetup}