Perhaps you should try some spelling variations:
thanh trung » thanh tung
thuyet hach » thuyet mach, thuyet xac, thuyet cac
thiet hach » thien hach, thiet hai, chiet tach
trung cua » truong cua, trung tuan, trung cap
dung cong » dung trong
dan than » dan chan, ban than, van than
than cau » toan cau, phan cau, than cap

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

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