Solution : https://service.sap.com/sap/support/notes/666508 (SAP Service marketplace login required)
Key words : 
'sap business partner enhancements', / check' tab -> 'foreign keys', select key field type ', foreign key definitions proposed, 'foreign key field', -key-fields/candidates', foreign keys, key table', proposed contents, select cardinality '
Related Notes : 
       
| 629487 | CRM 3.0 / CRM 3.1: Functional Enhancements | 
| 609514 | Changes in business partner CRM 3.0 SP15 and CRM 3.1 SP05 | 
| 598021 | Changes in business partner CRM 3.0 SP14 and CRM 3.1 SP04 |