Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
hanh dai » hanh tai, hanh dao, vanh dai
nam thuc » nam thuoc, am thuc, nam thu
sach hoi » sach doi, sach moi, cach thoi
hieu van » thien van, lieu va, hieu ve
tang ma » mang may, tang van
hieu va » lieu va, hieu qua
nang ma » sang ma, nang cao, mang may
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach

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 hoi ((nang ma) or (tang ma)) hoi. ((hieu van) or (hieu va)) nam thuc va hanh dai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoi ((nang ma) OR (tang ma)) hoi. ((hieu van) OR (hieu va)) nam thuc va hanh dai cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach hoi ((nang ma) or (tang ma)) hoi. ((hieu van) or (hieu va)) nam thuc va hanh dai cua viet*.