Perhaps you should try some spelling variations:
khong duong » khong dung, khong xuong, thong duong
thanh trung » thanh tung
hieu lang » chieu sang, hieu quang, nhieu tang
trung cua » truong cua, trung tuan, trung cap
cua khong » hua khong, cua phuong, cua thuong
duong dan » duong dang, huong dan, duong van
than cau » phan cau, than cap, thanh chau
toan cau » toan cao, toan ban, toan tap
he hieu » he nhieu, he dieu, de hieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: he hieu lang - thanh trung cua khong duong dan ((than cau) or (toan cau))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: he hieu lang - thanh trung cua khong duong dan ((than cau) OR (toan cau)).
• Adding a wildcard symbol may retrieve word variants: he hieu lang - thanh trung cua khong duong dan ((than cau) or (toan cau))*.