epub generation result has incorrect DocType

Hello,

I'm generating epub from Docbook input and getting during the validation one error and one warning with regards to the Doctype.

     [java] Epubcheck Version 3.0

     [java] Validating against EPUB version 2.0

     [java] ERROR: /home/vogella/workspace/docu/de.vogella.publishing/../output/epub/book.epub/OEBPS/content.opf: Obsolete or irregular DOCTYPE statement. The DOCTYPE can be removed.

     [java] WARNING: /home/vogella/workspace/docu/de.vogella.publishing/../output/epub/book.epub/OEBPS/toc.ncx: Irregular DOCTYPE: found '-//W3C//DTD XHTML 1.1//EN', expecting '<!DOCTYPE ncx PUBLIC "-//NISO//DTD ncx 2005-1//EN" "http://www.daisy.org/z3986/2005/ncx-2005-1.dtd">'.

My input looks simular to the XML file listed below.

Any advice how to remove this error? I'm using DocBook XSL 1.77 for the transformation.

Best regards, Lars

<?xml version="1.0"?>

<book>

	<bookinfo>

		<title>Java programming with the Eclipse IDE</title>

		<author>

			<firstname>Lars</firstname>

			<surname>Vogel</surname>

		</author>

		<copyright>

			<year>2007</year>

			<holder> Lars Vogel</holder>

		</copyright>

		<pubdate>17.02.2013</pubdate>

		<releaseinfo>Third edition

		</releaseinfo>

		<mediaobject role="cover">

			<imageobject id="cover-image">

				<imagedata fileref="images/cover.png" align="center" />

			</imageobject>

		</mediaobject>

	</bookinfo>

	<part>

		<title>Eclipse Overview</title>

		<chapter>

			<title>Eclipse overview

				and terminology

			</title>

			<para> This chapter gives a short introduction into

				the Eclipse

				project and the Eclipse IDE.

			</para>

                 </chapter>

       <part>

</book>