--- a/RelaxNG/publimeta.rnc	dim. mai 24 19:12:25 2015 +0200
+++ b/RelaxNG/publimeta.rnc	mer. mai 27 22:29:05 2015 +0200
@@ -38,7 +38,7 @@
 lang.attribute = attribute xml:lang { xsd:language }
 
 metadata.content =
-   (title, shorttitle?, subtitle*)?
+   (title & shorttitle? & subtitle*)?
  & identifier*
  & copyright*
  & collection?