Perhaps you should try some spelling variations:
tinh thong » tinh thuong, trinh thong, tinh khong
hieu luat » hieu qua
dung lam » dung luan, dung tai, dung dat
van hieu » cao hieu
van bien » van tien, vat bien, van kien
van hien » van tien
lam van » lam san, nam van, dam van

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( trinh dung lam van hieu luat ) or ( tinh thong quan ((van bien) OR (van hien)) so ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh dung lam van hieu luat ) OR ( tinh thong quan ((van bien) OR (van hien)) so )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( trinh dung lam van hieu luat ) or ( tinh thong quan ((van bien) OR (van hien)) so ))".
• Adding a wildcard symbol may retrieve word variants: (( trinh dung lam van hieu luat ) or ( tinh thong quan ((van bien) OR (van hien)) so ))*.