!doctype document type declaration
A valid Open eBook package file is a valid XML document and therefore optionally can contain document type declaration. If type declaration used, this must be a properly formatted document type:

<!DOCTYPE package PUBLIC "+//ISBN 0-9673008-1-9//DTD OEB 1.2 Package//EN" "http://openebook.org/dtds/oeb-1.2/oebpkg12.dtd">

For more information about DTDs, see the XML specification at http://www.w3.org/XML/.

attributes

version
specifies the Open eBook DTD document. This program support version 1.0.1 and 1.2.