Rezac (2008:26)

 The particle a is triggered by any preverbal nominal, regardless of whether it binds a resumptive or comes
 from any movement gap. 
 Yet a preverbal DP that comes from a movement gap only triggers (a)zo if it is the narrow subject, 
 and emañ, eo if it is a local object or a remote gap, (63) (cf. Hendrick 1988: 105-6 note 2). 
 
 Therefore the Leon dialect has the contrast in (64). 
 
 (64)a. A-bar extraction: DPi BE [… __i …]  →  eo/emañ copula / a particle
 
 (64)b. Broad subject: DPi BE [… pronouni …] → (a) zo copula / a particle (Leon dialect, setting aside narrow subject)
 
 
 Preverbal DPs other than the narrow subject are differentiated by the copula according as they link to a gap 
 or a resumptive, and the key to this difference is not in the particle, which neutralizes them.
 
 (63)a. Per EMAÑ / *A ZO Mona o klask __ er c'hoad.
 Per is R is Mona PRG seek in.the wood
 'Mona is looking for Per in the woods.' (Hendrick 1988: 105-6 note 2)
 
 (63)b. Per A ZO o klask Mona er c'hoad
 Per R is PRG seek Mona in.the wood
 'Per is looking for Mona in the woods.' (Hendrick 1988: 105-6 note 2)
 
 (63)c. Petra EMA en e zoñj [ober __]?
 what is in his thought do.INF
 'What is he thinking of doing.' (Fave 1998:141 [Leon])

Référence

• Rezac, M. 2008. ‘Building and interpreting a nonthematic A-position: A-resumption in English and Breton’, manuscrit à paraître dans Alain Rouveret (ed.), The Resumptive Book: Resumptive pronouns at the interfaces, Benjamins.