diff --git a/LDP/guide/docbook/Bash-Beginners-Guide/abook.xml b/LDP/guide/docbook/Bash-Beginners-Guide/abook.xml
index 3ab0721f..c3d2d8df 100644
--- a/LDP/guide/docbook/Bash-Beginners-Guide/abook.xml
+++ b/LDP/guide/docbook/Bash-Beginners-Guide/abook.xml
@@ -1,6 +1,6 @@
 <?xml version='1.0' encoding='UTF-8'?>
 <!DOCTYPE book PUBLIC "-//OASIS/DTD DocBook XML V4.1.2//EN"
-  "http://oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"
+  "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"
 [
 <!ENTITY chap1 SYSTEM "chap1.xml">
 <!ENTITY chap2 SYSTEM "chap2.xml">