Value MUST be part of code list 'Period Types' or 'UN/ECE Recommandation 20'.
ccv:Requirement/ccv:Response/cbc:Quantity
not(@unitCode) or (some $code in $clespd-PeriodMeasureTypeCodes satisfies $code = @unitCode) or (some $code in $clespd-UNECERec20 satisfies $code = @unitCode)