which subsidiary of international airlines group serves both barcelona–el prat airport and barcelona–el prat airport ?
select distinct var_uri where brack_open dbr_International_Airlines_Group dbo_subsidiary var_uri sep_dot var_uri dbo_targetAirport dbr_Barcelona–El_Prat_Airport sep_dot var_uri dbo_targetAirport dbr_Barcelona–El_Prat_Airport sep_dot brack_close