[1] [CITE@en[RFC 2440 - OpenPGP Message Format]]
([TIME[2015-02-15 14:39:41 +09:00]] 版)
<https://tools.ietf.org/html/rfc2440#section-6.2>

[2] [CITE@en[RFC 4880 - OpenPGP Message Format]]
([TIME[2015-04-05 14:41:03 +09:00]] 版)
<https://tools.ietf.org/html/rfc4880#section-6.2>

[3] [[PGPメッセージ交換形式]]

[4] [CITE@en[RFC 7681 - Email Exchange of Secondary School Transcripts]]
([TIME[2015-10-24 10:57:24 +09:00]] 版)
<https://tools.ietf.org/html/rfc7681>