code: protected String createExternalLinkElement(final DocBookVersion docBookVersion, final String title, final String url) {
          final StringBuilder linkEle = new StringBuilder();
          if (docBookVersion == DocBookVersion.DOCBOOK_50) {
              linkEle.append("<link xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"").append(url).append("\">");
              linkEle.append(title);
              linkEle.append("</link>");
          } else {
              linkEle.append("<ulink url=\"").append(url).append("\">");
              linkEle.append(title);
              linkEle.append("</ulink>");
          }
          return linkEle.toString();
      }
docs: Creates a string that represents an external link.
  
  @param docBookVersion The DocBook Version the link should be created for.
  @param title
  @param url            The links url.  @return