Fix typo reported in SF bug #427783.
diff --git a/Doc/ref/ref4.tex b/Doc/ref/ref4.tex
index 636bc1d..754a5b5 100644
--- a/Doc/ref/ref4.tex
+++ b/Doc/ref/ref4.tex
@@ -80,7 +80,7 @@
namespace of the module
\module{__builtin__}\refbimodindex{__builtin__}). The built-in
namespace associated with the execution of a code block is actually
-found by looking up the name \code{__builtins__} is its global
+found by looking up the name \code{__builtins__} in its global
namespace; this should be a dictionary or a module (in the latter case
its dictionary is used). Normally, the \code{__builtins__} namespace
is the dictionary of the built-in module \module{__builtin__} (note: