--- a/RelaxNG/publidoc.rnc	dim. oct. 23 16:45:12 2011 +0200
+++ b/RelaxNG/publidoc.rnc	dim. oct. 23 18:05:46 2011 +0200
@@ -457,7 +457,7 @@
    media.id.attribute,
    image.type?
 media.id.attribute = attribute id { xsd:NMTOKEN }
-image.type = attribute type { "thumbnail" }
+image.type = attribute type { "cover" | "thumbnail" }
 
 image.content =
    copyright?