Perhaps you should try some spelling variations:
hanh vai » hanh vi, hanh va, hanh tai
hieu van » thien van, lieu va, hieu ve
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
vai cua » dai cua, hai cua, lai cua
thuc va » thuc vat, thuc dan, thuc day
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
ty nang » ky nang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet
luc va » duc va, tuc va, loc va

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

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