a strategy for the expression of the necessarily shared participant in the relative clause of an externally headed - relative clause construction, in which the participant in the relative clause is expressed by a relative pronoun unique to the relative clause construction. Example: in He stole the emerald [which he gave to his wife], the relative clause is introduced by the relative pronoun which, which refers to the emerald, which is also expressed by the external relative clause head the emerald. The relative pronoun strategy is rare crosslinguistically, and largely restricted to the European area. (Section 19.2.2)