NOTE 2 A reference quantity value with associated measurement uncertainty is usually provided with reference to
a) material, e.g. a certified reference material,
b) a device, e.g. a stabilized laser,
d) a comparison of measurement standards.
ANNOTATION (informative) [2 December 2014] Here "quantity value" can be replaced by "value" without ambiguity: "value used as a basis for comparison with values of quantities of the same kind".