Perhaps you should try some spelling variations:
thanh trung » thanh tung
thiet hach » thien hach, thuyet hach, thiet hai
hoc thiet » hoc thieu, hoc thuyet, hoc hien
trung cua » truong cua, trung tuan, trung cap
dung cong » dung trong
dan toan » van toan, dan than, manh 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 thiet hach - thanh trung cua ((dung cong) or (dang cong)) dan toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thiet hach - thanh trung cua ((dung cong) OR (dang cong)) dan toan cau.
• Adding a wildcard symbol may retrieve word variants: hoc thiet hach - thanh trung cua ((dung cong) or (dang cong)) dan toan cau*.