private function findChildNodeWithKey($parentId, $key)
	{
        $result = array();
        $relations = $this->getRelations();

        if (isset($relations[RelationBuilder::TREE_PARAM_PARENTS][$parentId])) {
            foreach ($relations[RelationBuilder::TREE_PARAM_PARENTS][$parentId] as $id) {
                // Current found node
                $node = $relations[RelationBuilder::TREE_PARAM_ITEMS][$id][$key];

                $result = array_merge($result, $this->findChildNodeWithKey($id, $key));
                $result[] = $node;
            }
        }

        return $result;
    }