External reference: Add an external reference (optional) if you want to match the earnings account with the same account in another system. For instance, if you are an ad network working with publishing partners, and a publisher is registered in your invoicing system with customer ID 123456, then you can add 123456 as an external reference in Adnuntius. This way you can easily recognize two different entries as the same item across two different systems, which may in turn speed up processes like invoicing.