protected function parseSymbolsAfterDigits()
	{
		if (!$this->hasSingleQuote && !$this->hasDoubleQuote && strpos($this->text, 'x') === false)
		{
			return;
		}

		$map = [
			// 80's -- use an apostrophe
			"'s" => "\xE2\x80\x99",
			// 12' or 12" -- use a prime
			"'"  => "\xE2\x80\xB2",
			"' " => "\xE2\x80\xB2",
			"'x" => "\xE2\x80\xB2",
			'"'  => "\xE2\x80\xB3",
			'" ' => "\xE2\x80\xB3",
			'"x' => "\xE2\x80\xB3"
		];

		$regexp = "/[0-9](?>'s|[\"']? ?x(?= ?[0-9])|[\"'])/S";
		preg_match_all($regexp, $this->text, $matches, PREG_OFFSET_CAPTURE);
		foreach ($matches[0] as $m)
		{
			// Test for a multiply sign at the end
			if (substr($m[0], -1) === 'x')
			{
				$this->addTag($m[1] + strlen($m[0]) - 1, 1, "\xC3\x97");
			}

			// Test for an apostrophe/prime right after the digit
			$str = substr($m[0], 1, 2);
			if (isset($map[$str]))
			{
				$this->addTag($m[1] + 1, 1, $map[$str]);
			}
		}
	}