public function descendants($level = null)
	{
		$instance = self::blank();
		$instance->where('level', '>', $this->level)
		         ->order('lft', 'asc');

		if (isset($level))
		{
			$instance->where('level', '<=', $this->level + $level);
		}

		return $instance->where('lft', '>', $this->lft)
		                ->where('rgt', '<', $this->rgt)
		                ->applyScopesWhere($this);
	}