Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
danh vai » danh sai, danh va, doanh van
vai cua » dai cua, hai cua, lai cua
va danh » va dinh, va dan, va hanh
hieu va » lieu va, hieu qua
hieu ve » hieu van
sach tu » sach thu, cach tu, sach ty
tu nang » tru nang, tu nong, tu nano
cua te » cua tu
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: hoc sach tu nang ((xa hoi) or (o hoi)). ((hieu ve) OR (hieu va)) pham duc va danh vai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach tu nang ((xa hoi) OR (o hoi)). ((hieu ve) OR (hieu va)) pham duc va danh vai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach tu nang ((xa hoi) or (o hoi)). ((hieu ve) OR (hieu va)) pham duc va danh vai cua te".
• Adding a wildcard symbol may retrieve word variants: hoc sach tu nang ((xa hoi) or (o hoi)). ((hieu ve) OR (hieu va)) pham duc va danh vai cua te*.