public function toTable()
	{
		$code = "<table cellspacing=1 cellpadding=0>\n<tr><td colspan=2 align=center><hr>".$this->value."</td></tr>";
		if( $this->left || $this->right )
		{
			$code .= "<tr><td align=center valign=top>";
			if( $this->left )
				$code .= $this->left->toTable();
			else
				$code .= "&nbsp;";
			$code .= "</td><td align=center valign=top>";
			if( $this->right )
				$code .= $this->right->toTable();
			else
				$code .= "&nbsp;";
			$code .= "</td></tr>\n";
		}
		$code .= "</table>\n";
		return $code;
	}