Perhaps you should try some spelling variations:
thiet hach » thien hach, thuyet hach, thiet hai
hoc thiet » hoc thieu, hoc thuyet, hoc hien
tranh cua » doanh cua, manh cua
dung cong » dung trong
hach toan » thanh toan, manh toan
cua dung » cua dang, cua dong, qua dung
tap toan » tap doan, tap quan, bai 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 cong ((tap toan) OR (hach toan)) ban~.
• Adding a wildcard symbol may retrieve word variants: hoc thiet hach - canh tranh cua dung cong ((tap toan) or (hach toan)) ban*.