Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
hanh dai » hanh tai, hanh dao, vanh dai
so sach » so sanh, bo sach, co sach
truc va » thuc va, trung va
hieu ve » hieu va, hieu van
cao hoi » cau hoi, co hoi, cao hoc
su tien » su kien, su hien, tu tieng
dai su » dai sua, dai so, dan su

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach thu nang cao hoi. ((hieu ve) or (lieu va)) chat ((truc va) OR (thuc vat)) hanh dai su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach thu nang cao hoi. ((hieu ve) OR (lieu va)) chat ((truc va) OR (thuc vat)) hanh dai su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach thu nang cao hoi. ((hieu ve) or (lieu va)) chat ((truc va) OR (thuc vat)) hanh dai su tien".
• Adding a wildcard symbol may retrieve word variants: so sach thu nang cao hoi. ((hieu ve) or (lieu va)) chat ((truc va) OR (thuc vat)) hanh dai su tien*.