Also, some <guid> and <link> elements do not point to the same URL. This is a bad practice that should not be included in a specification.The <link> element should be removed or a 'isPermaLink="false"' attribute should be added to the <guid> element.
At the very least the urn <guid> needs an isPermaLink attribute set to false. Using a urn as a permalink is simply not valid.
Regards James
