check:
	find . -name "*.xml" -exec xmllint -valid -loaddtd -noout {} \; 2> errors
	if [ -s errors ] ; \
	 then \
	  echo ; \
	  echo "**************************************************" ; \
	  echo "There are validity errors. Check the file \"errors\"" ; \
	  echo "**************************************************" ; \
	 else \
	  rm errors ; \
	  echo ; \
	  echo "****************************" ; \
	  echo "All the documents are valid." ; \
	  echo "****************************" ; \
	fi