diff -r 91d67d2f121c -r cb6e0064c88c doc-src/TutorialI/CTL/PDL.thy
--- a/doc-src/TutorialI/CTL/PDL.thy	Thu Jan 19 21:22:29 2006 +0100
+++ b/doc-src/TutorialI/CTL/PDL.thy	Thu Jan 19 21:22:30 2006 +0100
@@ -12,7 +12,7 @@
 shown to be equivalent.}
 *}
 
-datatype formula = Atom atom
+datatype formula = Atom "atom"
                   | Neg formula
                   | And formula formula
                   | AX formula