Perhaps you should try some spelling variations:
thiet tach » chiet tach, thien hach, thuat tach
khong tang » khong cang, khong thanh, khong trong
hoc thiet » hoc thieu, hoc thuyet, hoc hien
tranh hua » tranh chua, tranh cua, tranh ha
hua khong » hoa khong, cua khong, hoac khong
tang dan » tang van, tung dan, tang luan
toan cao » toan ban
toan tap » toan ban

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 tach - canh tranh hua khong tang dan ((toan cao) OR (toan tap))~.
• Adding a wildcard symbol may retrieve word variants: hoc thiet tach - canh tranh hua khong tang dan ((toan cao) or (toan tap))*.