public function findSiteCandidatesForReference(NodeInterface $node, $userId)
    {
        $ne = $this
            ->db
            ->select('ucms_site_node', 'sn')
            ->where("sn.site_id = sa.site_id")
            ->condition('sn.nid', $node->id())
        ;
        $ne->addExpression('1');

        $idList = $this
            ->db
            ->select('ucms_site_access', 'sa')
            ->fields('sa', ['site_id'])
            ->condition('sa.uid', $userId)
            ->notExists($ne)
            ->groupBy('sa.site_id')
            ->execute()
            ->fetchCol()
        ;

        return $this->manager->getStorage()->loadAll($idList);
    }