Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
viec dat » vien dai, vien da, viec lam
sach thu » sach thue, sach thieu, sach tham
thuc van » thuc dan, thuc va, thuc hanh
hanh di » hanh vi, hanh de, hang di
sach ty » sach y, sach tu, xach tay
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ty) OR (sach thu)) nang xa hoi. hieu viec dat ((thuc van) or (thuc vat)) hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) nang xa hoi. hieu viec dat ((thuc van) OR (thuc vat)) hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach thu)) nang xa hoi. hieu viec dat ((thuc van) or (thuc vat)) hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) OR (sach thu)) nang xa hoi. hieu viec dat ((thuc van) or (thuc vat)) hanh di cua tre*.