Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
hanh dai » hanh tai, hanh dao, vanh dai
van hanh » van thanh, ban hanh, van anh
chat duc » chat xuc, chat doc, chet duoc
hieu cao » chieu cao, hieu cac, hieu ca
su sach » so sach, vu sach
duc van » duc va, duc tan, duc manh
cua tre » cua te, cuu tre, cua triet
mo hoc » mon hoc, co hoc
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: ((su sach) or (thuoc sach)) ky nang ((o hoi) or (mo hoc)). hieu cao chat duc van hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (thuoc sach)) ky nang ((o hoi) OR (mo hoc)). hieu cao chat duc van hanh dai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (thuoc sach)) ky nang ((o hoi) or (mo hoc)). hieu cao chat duc van hanh dai cua tre*.