Requirement that a business transaction be approved by at least two individuals.
SAP Help Portal website, [Using Dual Control for Bank Account Management](https://help.sap.com/viewer/ac319d8fa4ea4624b40a58d23e3c4627/1709%20000/en-US/ce3dba6c727849858fe7e0bc7e6e9480.html) (26.6.2019).
Based on Collins English dictionary, [Definition of 'four eyes principle'](https://www.collinsdictionary.com/dictionary/english/four-eyes-principle) (2.7.2019).