We from CEN-TC442-WG2/WG4 are proposing to change the reference to th…

Sections/Resource definition data schemas/Schemas/IfcMeasureResource/Documentation.md

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 The _IfcMeasureResource_ schema specifies units and defined measure types that may be assigned to quantities.
 
-> NOTE  The fundamental unit types used in this schema are based on the SI system defined in ISO 1000+A1, 1992, 1998. Units in measurement systems other than SI may be derived using this schema. Many definitions declared in the _IfcMeasureResource_ schema is adapted from [ISO 10303-41](../../bibliography.htm#iso-10303-41){ .int-ref}
+> NOTE  The fundamental unit types used in this schema are based on the SI system defined in ISO/IEC 80000-1:2009. Units in measurement systems other than SI may be derived using this schema. Many definitions declared in the _IfcMeasureResource_ schema is adapted from [ISO 10303-41](../../bibliography.htm#iso-10303-41){ .int-ref}
 
 > NOTE  In the definitions of the unit exponents the use of superscript font has been omitted. Therefore, m2 means square metre, m3 means cubic meter.
 
 In different types of units there are five basic cases:
 
-* Basic SI-units, which cover a number of fundamental units of mainly physical quantities defined by [ISO-1000](../../bibliography.htm#iso-1000){ .int-ref} such as meter or millimeter as unit for length measure or square meter as a unit for area measure. The unit may have a scaling prefix (for example: milli, kilo).
+* Basic SI-units, which cover a number of fundamental units of mainly physical quantities defined by [ISO/IEC 80000-1:2009](../../bibliography.htm#iso-1000){ .int-ref} such as meter or millimeter as unit for length measure or square meter as a unit for area measure. The unit may have a scaling prefix (for example: milli, kilo).
 * Derived SI-units, which are defined as a derivation of the basic SI-units, for example, Newton (kg m / s2) as a unit of force. Both basic and derived SI-units are in the IFCs represented by IfcSIUnit.
 * Conversion based units, which can be derived from SI-units by a scaling factor; e.g. inch which can be defined using SI-unit for length measure, i.e. an inch is 25.4 millimeters.
 * Derived units, which can be defined as a derivation or combination of a number of basic units. In a derived unit each of the basic unit "component" has a dimensional exponent in defining the derived unit; e.g. kg / m2, where kilogram (kg) has dimensional exponent 1 and meter (m) has exponent -2.