Perhaps you should try some spelling variations:
sach van » sach han, sach va, bach van
nam thuc » nam thuoc, am thuc, nam tu
hanh hai » thanh hai, nhanh hai, hang hai
so sach » so sanh, bo sach, co sach
mai hoi » mai khoi, dai hoi, lai hoi
lai roi » lai hoi, loi roi
hieu he » hieu ve, hiem he, hieu le
va hanh » van hanh, va thanh, va danh
hai cua » thai cua, dai cua, hoi cua

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 van ban ((mai hoi) or (lai roi)). hieu he ((nam thuc) OR (nam thu)) va hanh hai cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach van ban ((mai hoi) OR (lai roi)). hieu he ((nam thuc) OR (nam thu)) va hanh hai cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach van ban ((mai hoi) or (lai roi)). hieu he ((nam thuc) OR (nam thu)) va hanh hai cua vat".
• Adding a wildcard symbol may retrieve word variants: so sach van ban ((mai hoi) or (lai roi)). hieu he ((nam thuc) OR (nam thu)) va hanh hai cua vat*.