[1] X.501 : Information technology - Open Systems Interconnection - The Directory: Models (tsbmail 著, 2015-04-13 09:35:01 +09:00 版) <http://www.itu.int/rec/T-REC-X.501/en>

[2] DN

[3] X.501 : Information technology - Open Systems Interconnection - The Directory: Models (tsbmail著, 2018-08-12 00:44:20 +09:00) <https://www.itu.int/rec/T-REC-X.501/e>