Perhaps you should try some spelling variations:
thiet hach » thien hach, thuyet hach, thiet hai
dang thanh » dong thanh, dang hanh, hoang thanh
hoc thiet » hoc thieu, hoc thuyet, hoc hien
cua dung » cua dang, cua dong, cua rung
qua dung » quang dung, su dung, qua song
dan toan » van toan, dan than, manh toan

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

• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thiet hach - canh tranh ((cua dung) OR (qua dung)) cong ((dang thanh) OR (dan toan)) cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc thiet hach - canh tranh ((cua dung) OR (qua dung)) cong ((dang thanh) or (dan toan)) cao~".
• Adding a wildcard symbol may retrieve word variants: hoc thiet hach - canh tranh ((cua dung) OR (qua dung)) cong ((dang thanh) or (dan toan)) cao*.