Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu va » hieu qua
cac duc » cac du, cao duc, cac dac
y nang » ky nang, ly nang, v nang
va dan » ca dan, va dao, va dau
vi cua » vai cua
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach y nang x hoi. ((hieu va) or (lieu va)) cac duc va dan ((vi cua) or (di cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y nang x hoi. ((hieu va) OR (lieu va)) cac duc va dan ((vi cua) OR (di cua)) tre.
• Adding a wildcard symbol may retrieve word variants: thu sach y nang x hoi. ((hieu va) or (lieu va)) cac duc va dan ((vi cua) or (di cua)) tre*.