which subsidiary of flyi serves both washington dulles international airport and washington dulles international airport ?
select distinct var_uri where brack_open dbr_FLYi dbo_subsidiary var_uri sep_dot var_uri dbo_targetAirport dbr_Washington_Dulles_International_Airport sep_dot var_uri dbo_targetAirport dbr_Washington_Dulles_International_Airport sep_dot brack_close