Perhaps you should try some spelling variations:
thanh trung » thanh tung
thiet hach » thien hach, thuyet hach, chiet tach
thiet hai » thiet bi, thi hai, thien tai
trung va » truong va, trang va, trung ha
va trong » va truong, va thong, va tuong
cong dan » cong san, cong tan, huong dan
chan cao » chan cho, chay cao, toan cao
chat cao » chat co, chat cho, chat bao

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