Perhaps you should try some spelling variations:
quang trong » quang truong, quang trung, quan trong
dung ltrong » dung trong, dung trung, dung truong
dung luong » dung thuong, dung phuong, dung truong
hieu luat » hieu qua
trong van » trong cac
bien soan » bien so
van hieu » cao hieu
van bien » van tien, van hien, vat bien

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tin ((dung ltrong) or (dung luong)) van hieu luat ) or ( tinh quang trong van bien soan ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tin ((dung ltrong) OR (dung luong)) van hieu luat ) OR ( tinh quang trong van bien soan )).
• Adding a wildcard symbol may retrieve word variants: (( tin ((dung ltrong) or (dung luong)) van hieu luat ) or ( tinh quang trong van bien soan ))*.