Perhaps you should try some spelling variations:
trinh han » trinh quan
hieu soat » hieu suat, hieu hoat, hieu luat
tien soat » trien hoat, thien hoat, kiem soat
han lang » nhan lang, ban lang, ha lang
lang van » dang van, tang van, hoang van
van hieu » cao hieu
dung nam » dong nam, dung lam, sung nam
dung dat » dung va, dung tai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( trinh han lang van hieu soat ) or ( tin ((dung nam) or (dung dat)) toan tien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh han lang van hieu soat ) OR ( tin ((dung nam) OR (dung dat)) toan tien soat )).
• Adding a wildcard symbol may retrieve word variants: (( trinh han lang van hieu soat ) or ( tin ((dung nam) or (dung dat)) toan tien soat ))*.