Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
dai cuu » dai cua, dai huu
va hanh » van hanh, va thanh, va danh
va chao » va cao, va chat, va cham
hieu va » lieu va, hieu qua
cuu tre » cua tre, cau tren, cau treo
co hoi » co hoc, co loi
o hoi » o hoc, o hai, o hoa
xu va » xu van, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) ky nang ((o hoi) OR (co hoi)). hieu va chao xu va hanh dai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang ((o hoi) OR (co hoi)). hieu va chao xu va hanh dai cuu tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky nang ((o hoi) OR (co hoi)). hieu va chao xu va hanh dai cuu tre*".