text: timeline_balloons = $A()
  function attach_help_balloon(version_number, data_url) {
    node = $('version-'+version_number+'-icon');
    timeline_balloons[version_number] = new HelpBalloon({
      dataURL: data_url,
      icon: node,
      balloonPrefix: '/images/admin/balloon-',
      button: '/images/admin/button.png',
      contentMargin: 40,
      showEffect: Effect.Appear,
      hideEffect: Effect.Fade,
      autoHideTimeout: 2000
    });
  }
  function load_version_diff(url, diff_link) {
    popup = $('version-diff-popup');
    new Effect.Highlight(diff_link);
    req = new Ajax.Request(url, { method: 'get', evalScripts: true });
    return false;
  }
  