Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
hanh hai » thanh hai, nhanh hai, hang hai
thuc day » thuc dan, thuc vat
truc va » thuc va, thuc vat, trung va
hai cua » thai cua, dai cua, hoi cua
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
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)) dau ((truc va) or (thuc day)) hanh hai 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)) dau ((truc va) OR (thuc day)) hanh hai 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)) dau ((truc va) or (thuc day)) hanh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. ((hieu van) OR (hieu va)) dau ((truc va) or (thuc day)) hanh hai cua tre*.