e.g. -> e.g.,
diff --git a/Doc/ref/ref4.tex b/Doc/ref/ref4.tex
index 4873804..4d5f8d0 100644
--- a/Doc/ref/ref4.tex
+++ b/Doc/ref/ref4.tex
@@ -12,7 +12,7 @@
(like function bodies) may be executed many times. Code blocks may
textually contain other code blocks. Code blocks may invoke other
code blocks (that may or may not be textually contained in them) as
-part of their execution, e.g. by invoking (calling) a function.
+part of their execution, e.g., by invoking (calling) a function.
\index{code block}
\indexii{code}{block}