1. Faculty of Agriculture , University of Novi Sad , Trg D.Obradovica 8, Novi Sad , Serbia
2. Centre for Business and Economics Research , University of Coimbra and INESC Coimbra , Dias da Silva 165, 3004-512 Coimbra , Portugal
3. Polytechnic Institute of Bragança, Campus de Santa Apolónia , 5300-253 Bragança , Portugal