Perhaps you should try some spelling variations:
cach thuc » anh thuc, cac thu
van cach » va cach, van canh, vat cach
hieu van » hieu va, thien van, lieu va
xanh di » vanh dai, xanh tai
danh di » danh du, danh dien, danh gia
thuc va » thuc vat, thuc dan, thuc day
so sach » so sanh, bo sach, co sach
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet

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 y ((nang xa) or (nang ma)) hoi. hieu van cach thuc va ((danh di) or (xanh di)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((nang xa) OR (nang ma)) hoi. hieu van cach thuc va ((danh di) OR (xanh di)) cua tre.
• Adding a wildcard symbol may retrieve word variants: so sach y ((nang xa) or (nang ma)) hoi. hieu van cach thuc va ((danh di) or (xanh di)) cua tre*.