diff --git a/docs/develop/ports/arm/urls.txt b/docs/develop/ports/arm/urls.txt
index abaef44273..68a41c21f6 100644
--- a/docs/develop/ports/arm/urls.txt
+++ b/docs/develop/ports/arm/urls.txt
@@ -5,4 +5,7 @@ http://elinux.org/images/4/4e/Glikely-powerpc-porting-guide.pdf
 http://ols.fedoraproject.org/OLS/Reprints-2008/likely2-reprint.pdf
 http://www.bsdcan.org/2010/schedule/events/171.en.html
 http://www.devicetree.org/ (unofficial bindings)
+http://www.devicetree.org/Device_Tree_Usage
 http://elinux.org/Device_Trees
+* OF
+http://www.openfirmware.info/Bindings