Perhaps you should try some spelling variations:
thiet tach » chiet tach, thuat tach
thien hach » thien thanh, hien hanh
trinh xay » trinh ky
dung cong » dung trong
tran xay » tra xay, tran day, tran xuan
cong san » cong tac
san toan » van toan, dan toan, manh toan
toan cao » toan ban, toan tap

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 tach) or (thien hach)) - hanh ((tran xay) OR (trinh xay)) dung cong san toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((thiet tach) OR (thien hach)) - hanh ((tran xay) OR (trinh xay)) dung cong san toan cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((thiet tach) or (thien hach)) - hanh ((tran xay) OR (trinh xay)) dung cong san toan cao".
• Adding a wildcard symbol may retrieve word variants: hoc ((thiet tach) or (thien hach)) - hanh ((tran xay) OR (trinh xay)) dung cong san toan cao*.