CEPT Recommendation T/CD 06-01
CEPT Recommendation T/CD 06-01 was a standard set in 1981 by the European Conference of Postal and Telecommunications Administrations (CEPT) for the display of Videotex; specifically, for the Videotex Presentation Layer Data Syntax. It was revised a number of times in the 1980s, and also later redesignated as recommendation T/TE 06-01.
Source: Wikipedia — CEPT Recommendation T/CD 06-01 (CC BY-SA 4.0)