--- a/src/Doc/Tutorial/Advanced/simp2.thy Sun Jan 15 16:28:03 2023 +0100
+++ b/src/Doc/Tutorial/Advanced/simp2.thy Sun Jan 15 18:30:18 2023 +0100
@@ -122,7 +122,7 @@
rewrite rules. This is not quite true. For reasons of feasibility,
the simplifier expects the
left-hand side of each rule to be a so-called \emph{higher-order
-pattern}~@{cite "nipkow-patterns"}\indexbold{patterns!higher-order}.
+pattern}~\<^cite>\<open>"nipkow-patterns"\<close>\indexbold{patterns!higher-order}.
This restricts where
unknowns may occur. Higher-order patterns are terms in $\beta$-normal
form. (This means there are no subterms of the form $(\lambda x. M)(N)$.)