Principal Directorate Tools operates a computerised patent family system for documents in the search files published since 1968, which is linked with a class-inventory system (for older documents, written or typed lists are available). The family system is updated in co-operation with the national Offices on a basis of exchange of new input data. From these systems, examiners can obtain the identification of corresponding patents of other countries ("family members") and the classification given to a given patent document.