Perhaps you should try some spelling variations:
hieu nganh » vien nganh, hiem ngan, hieu manh
nang thanh » dang thanh, tang thanh, nhanh thanh
thanh tung » thanh cong
dang cong » dung cong
cong nang » cong ngang, cong lang, cong nong
trung va » truong va, trang va, trung ha
va dang » van dang, va nang, va lang

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((dieu hanh) or (hieu nganh)) - thanh trung va dang cong nang thanh tung~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((dieu hanh) OR (hieu nganh)) - thanh trung va dang cong nang thanh tung.
• Adding a wildcard symbol may retrieve word variants: doc ((dieu hanh) or (hieu nganh)) - thanh trung va dang cong nang thanh tung*.