code: protected Element createExternalLinkElement(final DocBookVersion docBookVersion, final Document document, String title,
              final String url) {
          final Element linkEle;
          if (docBookVersion == DocBookVersion.DOCBOOK_50) {
              linkEle = document.createElement("link");
              linkEle.setAttributeNS("http://www.w3.org/1999/xlink", "xlink:href", url);
          } else {
              linkEle = document.createElement("ulink");
              linkEle.setAttribute("url", url);
          }
          linkEle.setTextContent(title);
          return linkEle;
      }
docs: Creates an element that represents an external link.
  
  @param docBookVersion The DocBook Version the link should be created for.
  @param document       The document to create the link for.
  @param title
  @param url            The links url.  @return