SELECT DISTINCT C.ID_protocolli, C.oggetto_protocollo, C.data_protocollo, A1.nome_tree AS Mittente, A2.nome_tree AS Destinatario 
                FROM ((tab_tree AS A1 INNER JOIN tab_protocolli AS C ON A1.ID_tree = C.id_mittente) 
                INNER JOIN tab_tree AS A2 ON A2.ID_tree = C.id_destinatario)
                ORDER BY C.data_protocollo DESC