function buscar() {
      var form = document.forms['formulario'];
      var resultado = document.getElementById("resultado");
	  resultado.innerHTML= '<img src="imagenes/ajax-loader.gif">';
      var contenttype = 'application/x-www-form-urlencoded';
      var req;
      if (window.XMLHttpRequest) {
        req = new XMLHttpRequest();
      } else {
        req = new ActiveXObject("Microsoft.XMLHTTP");
      }
      req.open('POST', 'libreria/jsgmap/rdf.php', true);
      req.setRequestHeader('Content-Type', contenttype);
      req.onreadystatechange =
        function() {
          if (req.readyState == 4)
            resultado.innerHTML = req.responseText;
        }
      req.send('address=' + escape(form.direccion.value));
    }