diff -r 3b3cc0cf533f -r b44ad7e4c4d2 doc-src/TutorialI/Misc/natsum.thy
--- a/doc-src/TutorialI/Misc/natsum.thy	Mon Mar 19 13:05:56 2001 +0100
+++ b/doc-src/TutorialI/Misc/natsum.thy	Mon Mar 19 13:28:06 2001 +0100
@@ -59,7 +59,7 @@
 \end{warn}
 
 Simple arithmetic goals are proved automatically by both @{term auto} and the
-simplification methods introduced in \S\ref{sec:Simplification}.  For
+simplification method introduced in \S\ref{sec:Simplification}.  For
 example,
 *}