The 10-digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108. (However, the 9-digit SBN code was used in the United Kingdom until 1974.) An SBN may be converted to an ISBN by prepending the digit '0'. Currently, the ISO's TC 46/SC 9 is responsible for the ISBN. The ISO on-line facility only refers back to 1978.