$ISABELLE_HOME/src;

--- a/src/ZF/ROOT.ML	Thu Nov 20 15:48:32 1997 +0100
+++ b/src/ZF/ROOT.ML	Thu Nov 20 16:24:05 1997 +0100
@@ -30,7 +30,7 @@
 print_depth 1;
 
 (*Add user sections for inductive/datatype definitions*)
-use     "../Pure/section_utils.ML";
+use     "$ISABELLE_HOME/src/Pure/section_utils.ML";
 use     "thy_syntax.ML";
 
 use_thy "Let";