Perhaps you should try some spelling variations:
thieu tach » chiet tach, chieu sach, hieu cach
thien hach » thien thanh, hien hanh
cong thanh » dong thanh, cong trinh, cong tan
nang cong » nang song, dang cong, bang cong
cong van » cong vang, cong san, song van
van nang » van quang, van ban, van dong
cong cac » cuong cac, cong tac, cong cau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((thieu tach) or (thien hach)) - thanh cong van nang cong thanh cong cac~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((thieu tach) OR (thien hach)) - thanh cong van nang cong thanh cong cac.
• Adding a wildcard symbol may retrieve word variants: hoc ((thieu tach) or (thien hach)) - thanh cong van nang cong thanh cong cac*.