diff -r e9ab4ad7bd15 -r 23307fd33906 src/Doc/Tutorial/Rules/Force.thy
--- a/src/Doc/Tutorial/Rules/Force.thy	Thu Jan 11 13:48:17 2018 +0100
+++ b/src/Doc/Tutorial/Rules/Force.thy	Fri Jan 12 14:08:53 2018 +0100
@@ -15,20 +15,20 @@
 apply clarify
 oops
 
-text {*
+text \<open>
 proof\ {\isacharparenleft}prove{\isacharparenright}{\isacharcolon}\ step\ {\isadigit{1}}\isanewline
 \isanewline
 goal\ {\isacharparenleft}lemma{\isacharparenright}{\isacharcolon}\isanewline
 {\isacharparenleft}{\isasymforall}x{\isachardot}\ P\ x{\isacharparenright}\ {\isasymand}\ {\isacharparenleft}{\isasymexists}x{\isachardot}\ Q\ x{\isacharparenright}\ {\isasymlongrightarrow}\ {\isacharparenleft}{\isasymforall}x{\isachardot}\ P\ x\ {\isasymand}\ Q\ x{\isacharparenright}\isanewline
 \ {\isadigit{1}}{\isachardot}\ {\isasymAnd}x\ xa{\isachardot}\ {\isasymlbrakk}{\isasymforall}x{\isachardot}\ P\ x{\isacharsemicolon}\ Q\ xa{\isasymrbrakk}\ {\isasymLongrightarrow}\ P\ x\ {\isasymand}\ Q\ x
-*}
+\<close>
 
-text {*
+text \<open>
 couldn't find a good example of clarsimp
 
 @{thm[display]"someI"}
 \rulename{someI}
-*}
+\<close>
 
 lemma "\<lbrakk>Q a; P a\<rbrakk> \<Longrightarrow> P (SOME x. P x \<and> Q x) \<and> Q (SOME x. P x \<and> Q x)"
 apply (rule someI)
@@ -38,13 +38,13 @@
 apply (fast intro!: someI)
 done
 
-text{*
+text\<open>
 proof\ {\isacharparenleft}prove{\isacharparenright}{\isacharcolon}\ step\ \isadigit{1}\isanewline
 \isanewline
 goal\ {\isacharparenleft}lemma{\isacharparenright}{\isacharcolon}\isanewline
 {\isasymlbrakk}Q\ a{\isacharsemicolon}\ P\ a{\isasymrbrakk}\ {\isasymLongrightarrow}\ P\ {\isacharparenleft}SOME\ x{\isachardot}\ P\ x\ {\isasymand}\ Q\ x{\isacharparenright}\ {\isasymand}\ Q\ {\isacharparenleft}SOME\ x{\isachardot}\ P\ x\ {\isasymand}\ Q\ x{\isacharparenright}\isanewline
 \ \isadigit{1}{\isachardot}\ {\isasymlbrakk}Q\ a{\isacharsemicolon}\ P\ a{\isasymrbrakk}\ {\isasymLongrightarrow}\ P\ {\isacharquery}x\ {\isasymand}\ Q\ {\isacharquery}x
-*}
+\<close>
 
 end