diff -r 527811f00c56 -r 2f98365f57a8 doc-src/TutorialI/Rules/rules.tex
--- a/doc-src/TutorialI/Rules/rules.tex	Wed Jul 31 16:10:24 2002 +0200
+++ b/doc-src/TutorialI/Rules/rules.tex	Wed Jul 31 17:42:38 2002 +0200
@@ -4,7 +4,7 @@
  
 This chapter outlines the concepts and techniques that underlie reasoning
 in Isabelle.  Until now, we have proved everything using only induction and
-simplification, but any serious verification project require more elaborate
+simplification, but any serious verification project requires more elaborate
 forms of inference.  The chapter also introduces the fundamentals of
 predicate logic.  The first examples in this chapter will consist of
 detailed, low-level proof steps.  Later, we shall see how to automate such