Add a usepackage{url}

diff --git a/docs/ext-core/core.tex b/docs/ext-core/core.tex
index d03f764..0ee5cde 100644 (file)
--- a/docs/ext-core/core.tex
+++ b/docs/ext-core/core.tex
@@ -2,6 +2,7 @@
 \usepackage{a4wide}
 \usepackage{code}
 \usepackage{natbib}
+\usepackage{url}
 
 \sloppy
 \setlength{\parskip}{0.5\baselineskip plus 0.2\baselineskip minus 0.1\baselineskip}