Perhaps you should try some spelling variations:
thanh trung » thanh tung
chiet tach » chieu sach
thien hach » thien thanh, hien hanh
trung cao » truong cao, trung cap, trung co
han cong » phan cong, hang cong, hanh cong
dan toan » van toan, manh toan, xuan toan
dan than » dan chan, ban than, van than
cao han » cao nhan, cao phan, cao van

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((chiet tach) or (thien hach)) - thanh trung cao han cong ((dan toan) OR (dan than)) cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((chiet tach) OR (thien hach)) - thanh trung cao han cong ((dan toan) OR (dan than)) cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((chiet tach) or (thien hach)) - thanh trung cao han cong ((dan toan) OR (dan than)) cao".
• Adding a wildcard symbol may retrieve word variants: hoc ((chiet tach) or (thien hach)) - thanh trung cao han cong ((dan toan) OR (dan than)) cao*.