# F-LIB240

Source: https://xmlvalid.com/rules/F-LIB240

> No more than one ContractDocumentReference class may be present

- Level: error
- Rule sets: OIOUBL 2.1 Invoice rules (Denmark) 1.17.2, OIOUBL 2.1 Credit Note rules (Denmark) 1.17.2, OIOUBL 2.1 Reminder rules (Denmark) 1.17.2
- Test: `count(cac:ForeignExchangeContract/cac:ContractDocumentReference) > 1`

Validate a document against these rules: https://xmlvalid.com/validate