Perhaps you should try some spelling variations:
thanh trung » thanh tung
chieu sang » chieu xanh, hieu lang, nhieu tang
chieu sach » chinh sach, chiet tach, chieu xanh
trung cua » truong cua, trung tuan, trung cap
ban dung » van dung, dan dung, tan dung
dung bai » dung tai, dung sai, dung hai
bai toan » bai tap
toan cau » toan cao, toan ban, toan tap

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((chieu sang) or (chieu sach)) - thanh trung cua ban dung bai toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((chieu sang) OR (chieu sach)) - thanh trung cua ban dung bai toan cau.
• Adding a wildcard symbol may retrieve word variants: hoc ((chieu sang) or (chieu sach)) - thanh trung cua ban dung bai toan cau*.