Parsing rss feed. Some fields undefined

I am attempting to parse this rss feed - http://www.spiegel.de/international/germany/index.rss

I am using the following code to parse it:

 $.ajax({        url      : document.location.protocol +'//ajax.googleapis.com/ajax/services/feed/load?v=1.0&num=10&callback=?&q='+        encodeURIComponent('http://www.spiegel.de/international/germany/index.rss'),        dataType : 'json',        success  : function (data) {          if (data.responseData.feed && data.responseData.feed.entries) {            $.each(data.responseData.feed.entries, function (i, e) {              console.log("------------------------");              console.log("title      : "+ e.title);              console.log("link      : "+ e.link);              console.log("pubDate     : "+ e.pubDate);              console.log("description     : "+ e.description);              console.log("pubDate     : "+ e.pubDate);              console.log("guid: "+ e.guid);            });          }        }      });

In the console.log only the title and the link appear. The description, pubDate and guid are all undefined.

Could someone be so kind as to explain what I am doing wrong?