*仕様書

- [1] [CITE@en[RFC 3490 - Internationalizing Domain Names in Applications (IDNA)]] 
<http://tools.ietf.org/html/rfc3490>
- [2] [CITE@en[RFC 3491 - Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN)]] 
<http://tools.ietf.org/html/rfc3491>
- [3] [CITE@en[RFC 3492 - Punycode: A Bootstring encoding of Unicode for Internationalized Domain Names in Applications (IDNA)]] 
<http://tools.ietf.org/html/rfc3492>