 It became the basis for a standard (ISO 226) that was considered definitive until 2003 when ISO revised the standard on the basis of recent assessments by research groups worldwide.Perceived discrepancies between early and more recent determinations led the International Organization for Standardization (ISO) to revise the standard curves in ISO 226.They did this in response to recommendations in a study coordinated by the Research Institute of Electrical Communication, Tohoku University, Japan.