Perhaps you should try some spelling variations:
thanh tung » thanh cong
thong cong » trong cong, tong cong, thong thong
hieu lang » chieu sang, hieu quang, nhieu tang
cua thong » cua thuong, cua khong, cua tong
nhanh cau » nhanh cay, thanh chau, nhanh ha
hoc hieu » hoc thieu, hoc hien, doc hieu
cong tan » cong tac, cong san, cong thanh
phan cau » phan dau, phan cac, phan tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc hieu lang - ((thanh trung) OR (thanh tung)) cua thong cong tan ((nhanh cau) or (phan cau))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu lang - ((thanh trung) OR (thanh tung)) cua thong cong tan ((nhanh cau) OR (phan cau)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu lang - ((thanh trung) OR (thanh tung)) cua thong cong tan ((nhanh cau) or (phan cau))".
• Adding a wildcard symbol may retrieve word variants: hoc hieu lang - ((thanh trung) OR (thanh tung)) cua thong cong tan ((nhanh cau) or (phan cau))*.