Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
hanh dai » hanh tai, hanh dao, vanh dai
nam thuc » nam thuoc, am thuc, nam thu
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
su sach » so sach, vu sach
va nam » van nam, ha nam, va nay
o hoi » co hoi, o hoc, o hoa
o hai » co hai, so hai, o lai

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

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