Index: /trunk/data/maps.xsd
===================================================================
--- /trunk/data/maps.xsd	(revision 7752)
+++ /trunk/data/maps.xsd	(revision 7753)
@@ -618,4 +618,6 @@
 						<!-- The area of use, e.g. <bounds min-lat='45.7' min-lon='5.9' max-lat='55.0' max-lon='17.3'/> -->
 						<xs:element name="bounds" minOccurs="0" maxOccurs="1" type="tns:bounds" />
+						<!-- Provide a source that this background can be used for OSM. A page on the OSM-wiki with additional explanation and further references is preferred, but other sources (for example the license text) can also be linked. -->
+						<xs:element name="permission-ref" minOccurs="0" maxOccurs="1" type="xs:anyURI" />
 						<!-- A link to an EULA text that has to be accepted by the user, before the imagery source is added. -->
 						<xs:element name="eula" minOccurs="0" maxOccurs="1" type="tns:eula" />