name the office holder whose predecessor is alfred milner and successor is herbert samuel ?
SELECT DISTINCT var_uri where brack_open var_uri dbp_predecessor dbr_Alfred_Milner,_1st_Viscount_Milner sep_dot var_uri dbp_successor dbr_Herbert_Samuel,_1st_Viscount_Samuel sep_dot var_uri a dbo_OfficeHolder brack_close