A **catalogued quantity-kind**: a {dimensioned kind} together with its exact
source in the 80000 series — the part, the printed item designation, the principal
quantity symbol, and the coherent SI unit symbol. Every field other than `qk` is a
*citation locator*; the citation travels with the kind as data, so a downstream
model can render or audit the source of each definition. Shared by every part
module, so the structure is defined once rather than per part. 

ref : PropertyKindCalculus.Iso80000.StandardRef

The part of the series this kind is defined in. 

item : String

The item designation as printed, e.g. "3-3". 

symbol : String

The principal quantity symbol, e.g. "A". 

coherentUnit : String

The coherent SI unit symbol, e.g. "m²" (a citation locator). 

qk : PropertyKindCalculus.DimensionedKind LTMCTDimensionBase

The dimensioned kind itself.