Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
day xanh » day manh, cay xanh, day danh
thuc day » thuc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
hieu van » thien van, lieu va, hieu ve
hieu va » lieu va, hieu qua
xanh di » danh di, vanh dai, xanh tai
tu sach » thu sach, su sach, te sach
nang ma » tang ma, sang ma, nang cao
lo nang » ho nang, ly nang, loai nang
ma hoi » mai hoi, xa hoi, ma hoa
di cua » dai cua, doi cua, de cua

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