This standard gives the rules for the use of the International System of Units, as to how derived units of SI may be formed and for forming and selecting decimal multiples and sub-multiples of the SI units for application in the various fields with SI units.
1.2 It includes reference also to certain other units which are not within the International System but which at this stage have been recognized for use in association with SI units.
SS 52-1971 history
1971SS 52-1971 RULES FOR THE USE OF UNITS OF THE INTERNATIONAL SYSTEM (SI)