Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » thien van, lieu va, hieu ve
truc vat » thuc vat, truc va, truc van
vat hanh » vat thanh, van hanh, va hanh
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
vi cua » vai cua, di cua
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach y nang ((x ho) or (o hoi)). ((hieu van) or (hieu va)) cau truc vat hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y nang ((x ho) OR (o hoi)). ((hieu van) OR (hieu va)) cau truc vat hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: thu sach y nang ((x ho) or (o hoi)). ((hieu van) or (hieu va)) cau truc vat hanh vi cua tre*.