Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thanh vi » hanh vi, thanh va, thanh ve
thuc va » thuc dan, thuc day
van hac » van hoc, van ha, van hai
sach ty » sach y, sach tu, sach thu
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
vi cua » vai cua, di cua

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

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