/**
  * override fetch()
  *
  */
 function fetch()
 {
     if (empty($this->_isbn)) {
         $this->_error_message = 'ISBN does not set';
         return false;
     }
     return parent::fetch();
 }
 function XooNIps_PubMed_JournalEsummary()
 {
     // call parent constructor
     parent::XooNIpsXMLParser();
     // set fetcher conditions
     $this->_fetch_url = 'http://eutils.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi';
     $this->_fetch_arguments['db'] = 'journals';
     $this->_fetch_arguments['retmode'] = 'xml';
     // set parser conditions
     $this->_parser_doctype = 'eSummaryResult';
     $this->_parser_public_id = '-//NLM//DTD eSummaryResult, 29 October 2004//EN';
 }