What vfl club(s) for players ranked sergeant, 8th brigade australian field artillery at time of death?
create table table_16527640_2 (vfl_club_s_ varchar, rank_held_at_time_of_death varchar, PRIMARY KEY (vfl_club_s_))
select vfl_club_s_ from table_16527640_2 where rank_held_at_time_of_death = "sergeant, 8th brigade australian field artillery"