 Although it was soon recognized in 1966 that a five character CODEN would not be sufficient to provide all future periodical titles with CODEN, it was still defined as a five character code as given in ASTM standard E250 until 1972.In 1976 the ASTM standard E250-76 defined a six-character CODEN.Beginning in the year 1975, the CODEN system was within the responsibility of the American Chemical Society.