function Buscar(){

    if ( ( document.formulario.busqueda.value == null ) || document.formulario.busqueda.value == "" ) {
	alert("Indique alguna palabra de búsqueda");
	document.formulario.busqueda.focus();
    } else {
	document.formulario.submit();
    }

}
function ValidarCamposCumplimentados (formul) {

    if (((formul.coberturaespacial.value == null ) || (formul.coberturaespacial.value == "" )) &&
	((formul.p_clave.value == null ) || (formul.p_clave.value == "" )) &&
	((formul.keywords_no.value == null ) || (formul.keywords_no.value == "" )) &&
	((formul.title.value == null ) || (formul.title.value == "" )) &&
	((formul.autor.value == null ) || (formul.autor.value == "" )) &&
	((formul.categoria.value == null ) || (formul.categoria.value == "" )) &&
	((formul.subcategoria.value == null ) || (formul.subcategoria.value == "" ))) 	
    {
	alert("Indique algún criterio de búsqueda");
	formul.coberturaespacial.focus();
    } else {
	formul.submit();
    }

}