diff -r c8a2755bf220 -r ff784d5a5bfb src/Doc/Tutorial/Misc/Tree.thy
--- a/src/Doc/Tutorial/Misc/Tree.thy	Sat Jan 05 17:00:43 2019 +0100
+++ b/src/Doc/Tutorial/Misc/Tree.thy	Sat Jan 05 17:24:33 2019 +0100
@@ -13,7 +13,7 @@
 "mirror (Node l x r) = Node (mirror r) x (mirror l)"(*>*)
 
 text\<open>\noindent
-Define a function @{term"mirror"} that mirrors a binary tree
+Define a function \<^term>\<open>mirror\<close> that mirrors a binary tree
 by swapping subtrees recursively. Prove
 \<close>
 
@@ -28,7 +28,7 @@
 (*>*)
 
 text\<open>\noindent
-Define a function @{term"flatten"} that flattens a tree into a list
+Define a function \<^term>\<open>flatten\<close> that flattens a tree into a list
 by traversing it in infix order. Prove
 \<close>