The name of the relation that defines the unique or primary key definition which is referred to by a foreign key of this relation. If there are no referenced-field-names specified with this relation-name, then the referenced-relation must have an associated constraint which specifies a primary key. If there are referenced-field-names, the referenced-relation must have a unique or primary key constraint defined which specifies a list of unique-field-names. These names have to be the same names as in the referenced-relation.