Perhaps you should try some spelling variations:
thiet tach » chiet tach, thien hach, thuat tach
hoc thiet » hoc thieu, hoc thuyet, hoc hien
nang cong » nang song, bang cong, hang cong
dang cong » dung cong
van thanh » ban thanh, van tuan
tang van » dang van, hoang van, trong van
tang va » trang va, thang va, tang vat

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 - hanh ((tang va) or (tang van)) ((nang cong) OR (dang cong)) van thanh san~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thiet tach - hanh ((tang va) OR (tang van)) ((nang cong) OR (dang cong)) van thanh san.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc thiet tach - hanh ((tang va) or (tang van)) ((nang cong) OR (dang cong)) van thanh san".
• Adding a wildcard symbol may retrieve word variants: hoc thiet tach - hanh ((tang va) or (tang van)) ((nang cong) OR (dang cong)) van thanh san*.