protected function coreCommand($command, $core, $params = array())
    {
        $command = strtoupper($command);
        $params = array_merge($params, array('action' => $command, 'wt' => 'json'));
        $params[$command == 'CREATE' ? 'name' : 'core'] = $core;

        return $this->_sendRawGet($this->_constructUrl('admin/cores', $params));
    }