--- a/src/HOL/IMP/Sec_Typing.thy Sat Jan 05 17:00:43 2019 +0100
+++ b/src/HOL/IMP/Sec_Typing.thy Sat Jan 05 17:24:33 2019 +0100
@@ -178,7 +178,7 @@
subsubsection "The Standard Typing System"
-text\<open>The predicate @{prop"l \<turnstile> c"} is nicely intuitive and executable. The
+text\<open>The predicate \<^prop>\<open>l \<turnstile> c\<close> is nicely intuitive and executable. The
standard formulation, however, is slightly different, replacing the maximum
computation by an antimonotonicity rule. We introduce the standard system now
and show the equivalence with our formulation.\<close>