[ibr-085]-Start date of line period (ibt-134) MUST be within invoice period (ibg-14).
ibr-085
cac:InvoiceLine/cac:InvoicePeriod | cac:CreditNoteLine/cac:InvoicePeriod
(cbc:StartDate >= xs:date(../../cac:InvoicePeriod/cbc:StartDate)) or not(cbc:StartDate) or not(../../cac:InvoicePeriod/cbc:StartDate)