The purchase order number set by the buyer

retann_Required
No
retann_Examples
 <documentReference documentType="BuyerOrder" id="555666" date="2020-12-01"> 
retann_Xpath
/b24Message/returnAnnouncement/documentReference[@documentType="BuyerOrder"]/@id
retann_Sort
1900
retann_Id
10
retann_Type
Text