Perhaps you should try some spelling variations:
thiet hach » thien hach, thuyet hach, thiet hai
truong cao » truong dai
nhung song » nhung cong, nhung bong, nhung chong
hoc thiet » hoc thieu, hoc thuyet, hoc hien
trung cua » truong cua, trung tuan, trung cap
song van » hoang van, trong van, duong van
toan cao » toan tap
toan ban » van 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 hach - thanh ((trung cua) OR (truong cao)) nhung song van ((toan cao) OR (toan ban))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc thiet hach - thanh ((trung cua) or (truong cao)) nhung song van ((toan cao) OR (toan ban))~".
• Adding a wildcard symbol may retrieve word variants: hoc thiet hach - thanh ((trung cua) or (truong cao)) nhung song van ((toan cao) OR (toan ban))*.