doc-src/TutorialI/todo.tobias

--- a/doc-src/TutorialI/todo.tobias	Wed Jan 24 11:59:15 2001 +0100
+++ b/doc-src/TutorialI/todo.tobias	Wed Jan 24 12:29:10 2001 +0100
@@ -89,10 +89,10 @@
 ==================
 
 Exercises
-%\begin{exercise}
-%Extend expressions by conditional expressions.
-braucht wfrec!
-%\end{exercise}
+
+For extensionality (in Sets chapter): prove
+valif o norm = valif
+in If-expression case study (Ifexpr)
 
 Nested inductive datatypes: another example/exercise:
  size(t) <= size(subst s t)?