[1] [CITE@en[RFC 5070 - The Incident Object Description Exchange Format]]
([TIME[2017-05-07 20:04:30 +09:00]])
<https://tools.ietf.org/html/rfc5070#section-2.9>

[2] [CITE@en[RFC 7970 - The Incident Object Description Exchange Format Version 2]]
([TIME[2017-05-14 16:49:04 +09:00]])
<https://tools.ietf.org/html/rfc7970#section-2.8>