public function previous($field = 'datepublish', $where = [])
{
list($field, $asc) = $this->app['storage']->getSortOrder($field);
$operator = $asc ? '<' : '>';
$order = $asc ? ' DESC' : ' ASC';
$params = [$field => $operator . $this->values[$field], 'limit' => 1, 'order' => $field . $order, 'returnsingle' => true, 'hydrate' => true];
$pager = [];
$previous = $this->app['storage']->getContent($this->contenttype['singular_slug'], $params, $pager, $where);
return $previous;
}