which subsidiary of air china serves both sunan shuofang international airport and beijing capital international airport ?
select distinct var_uri where brack_open dbr_Air_China dbo_subsidiary var_uri sep_dot var_uri dbo_targetAirport dbr_Sunan_Shuofang_International_Airport sep_dot var_uri dbo_targetAirport dbr_Beijing_Capital_International_Airport sep_dot brack_close