In 1997, to overcome these difficulties, the International Organization for Standardization (ISO) published ISO 13616:1997. This proposal had a degree of flexibility that the European Committee for Banking Standards (ECBS) believed would make it unworkable, and they produced a "slimmed down" version of the standard which, amongst other things, permitted only upper-case letters and required that the IBAN for each country have a fixed length. ISO 13616:1997 was subsequently withdrawn and replaced by ISO 13616:2003. The standard was revised again in 2007 when it was split into two parts. ISO 13616-1:2007 "specifies the elements of an international bank account number (IBAN) used to facilitate the processing of data internationally in data interchange, in financial environments as well as within and between other industries" but "does not specify internal procedures, file organization techniques, storage media, languages, etc. to be used in its implementation". ISO 13616-2:2007 describes "the Registration Authority (RA) responsible for the registry of IBAN formats that are compliant with ISO 13616-1 the procedures for registering ISO 13616-compliant IBAN formats". The official IBAN registrar under ISO 13616-2:2007 is SWIFT.