Perhaps you should try some spelling variations:
hanh trung » thanh trung, hanh trang, manh trung
chieu sach » chinh sach, chiet tach, chieu sang
hieu lang » chieu sang, hieu quang, nhieu tang
cong tan » cong tac, cong san, cong thanh
tan toan » tan tran, tap toan, van toan
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 ((hieu lang) or (chieu sach)) - hanh trung ((cua nhung) OR (va nhung)) cong tan toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu lang) OR (chieu sach)) - hanh trung ((cua nhung) OR (va nhung)) cong tan toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu lang) or (chieu sach)) - hanh trung ((cua nhung) OR (va nhung)) cong tan toan cau".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu lang) or (chieu sach)) - hanh trung ((cua nhung) OR (va nhung)) cong tan toan cau*.