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

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