Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thu nang » thu hang, thu bang, tho nang
hanh dai » hanh tai, hanh dao, vanh dai
thi nang » thi cong, ki nang, thi hanh
va hanh » van hanh, va thanh, va danh
cac dac » cac dan, cac dai, cac bac
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac nuoc
cua tre » cua te, cuu tre, cua triet

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 ((thu nang) or (thi nang)) xa hoi. hieu va ((cac duc) OR (cac dac)) va hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((thu nang) OR (thi nang)) xa hoi. hieu va ((cac duc) OR (cac dac)) va hanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((thu nang) or (thi nang)) xa hoi. hieu va ((cac duc) OR (cac dac)) va hanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ((thu nang) or (thi nang)) xa hoi. hieu va ((cac duc) OR (cac dac)) va hanh dai cua tre*.