[2] RFC 1386 - The US Domain, 2021-02-01T01:57:29.000Z, 2021-03-13T09:59:49.275Z https://tools.ietf.org/html/rfc1386
[1] RFC 1480 - The US Domain (2015-05-03 16:36:03 +09:00 版) http://tools.ietf.org/html/rfc1480