Perhaps you should try some spelling variations:
khien tinh » thien tinh, khien thich, bien tinh
hien tinh » thien tinh, bien tinh, dien tinh
manh hung » anh huong
hung tuan » hung tran, quang tuan, trung tuan
dung cong » dung trong
tap toan » tap doan, tap quan, bai toan
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 ((hien tinh) OR (khien tinh)) - manh hung tuan ((dang cong) or (dung cong)) tap toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hien tinh) OR (khien tinh)) - manh hung tuan ((dang cong) OR (dung cong)) tap toan cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hien tinh) OR (khien tinh)) - manh hung tuan ((dang cong) or (dung cong)) tap toan cao".
• Adding a wildcard symbol may retrieve word variants: hoc ((hien tinh) OR (khien tinh)) - manh hung tuan ((dang cong) or (dung cong)) tap toan cao*.