According to the Act concerning units of measurement dated 2 July 1969 (Federal Law Gazette I, page 709-712) and the implementing regulation of 26 June 1970 (Federal Law Gazette I, page 981), SI units (Système International d'Unités) combined with signs of the decimal system have been the only legally valid units since 31 December 1977. DIN 1301, Part1, December 1985, Units, Unit Names and Unit Signs lists the presently permissible units. Conversion factors for those units whose use is no longer allowed can be found in DIN 1301, Part 3 and under pressure in this book; see also conversion of British and U.S. units into metric units.