see 1. Preparation of Internationalized Strings ("stringprep") => https://tools.ietf.org/html/rfc3454 2. Lightweight Directory Access Protocol (LDAP): Internationalized String Preparation https://tools.ietf.org/rfc/rfc4518.txt 3. unicode 'internationalization' FAQ => http://unicode.org/faq/internationalization.html
see
Preparation of Internationalized Strings ("stringprep") => https://tools.ietf.org/html/rfc3454
Lightweight Directory Access Protocol (LDAP): Internationalized String Preparation https://tools.ietf.org/rfc/rfc4518.txt
unicode 'internationalization' FAQ => http://unicode.org/faq/internationalization.html