Perhaps you should try some spelling variations:
sach dao » lanh dao
dao sang » cao sang, dao khang, dao quang
hieu van » thien van, lieu va, hieu ve
nam thuc » nam thuoc, am thuc, nam thu
thuc dan » thuc hanh, hoc dan, thuc vat
dan hanh » dang hanh, dan khanh, dan thanh
hanh dai » hanh tai, hanh dao, vanh dai
cua viet » ca viet, hoa viet, cua dieu
tu sach » thu sach, su sach, te sach
sang ma » tang ma, nang ma, sang tao
hieu va » lieu va, hieu qua
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach dao sang ma hoi. ((hieu van) or (hieu va)) nam thuc dan hanh dai ((cua viet) OR (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach dao sang ma hoi. ((hieu van) OR (hieu va)) nam thuc dan hanh dai ((cua viet) OR (cua vat)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach dao sang ma hoi. ((hieu van) or (hieu va)) nam thuc dan hanh dai ((cua viet) OR (cua vat))".
• Adding a wildcard symbol may retrieve word variants: tu sach dao sang ma hoi. ((hieu van) or (hieu va)) nam thuc dan hanh dai ((cua viet) OR (cua vat))*.