what are the airlines whose hub airport is operated by the aeroporto guglielmo marconi di bologna ?
SELECT DISTINCT var_uri where brack_open var_x dbo_operator dbr_Aeroporto_Guglielmo_Marconi_di_Bologna_ attr_open company attr_close sep_dot var_uri dbo_hubAirport var_x sep_dot var_uri a dbo_Airline brack_close