Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
danh dai » danh dau, danh di, danh sai
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
va danh » va dinh, va dan, va hanh
cua tre » cua te, cuu tre, cua triet
te cac » tu cac, ve cac, te cao
x hoi » xa hoi, o hoi, 5 hoi
va am » va lam, va cam

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) or (te cac)) ky nang ((x hoi) OR (x ho)). hieu va am thuc va danh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (te cac)) ky nang ((x hoi) OR (x ho)). hieu va am thuc va danh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (te cac)) ky nang ((x hoi) OR (x ho)). hieu va am thuc va danh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (te cac)) ky nang ((x hoi) OR (x ho)). hieu va am thuc va danh dai cua tre*.