what is the military unit whose command structures are 21st sustainment command and 21st sustainment command ?
SELECT DISTINCT var_uri where brack_open var_uri dbo_commandStructure dbr_21st_Sustainment_Command_ attr_open Theater attr_close sep_dot var_uri dbo_commandStructure dbr_21st_Sustainment_Command_ attr_open Theater attr_close sep_dot var_uri a dbo_MilitaryUnit brack_close