Perhaps you should try some spelling variations:
cach thoi » cac thoi, cach thuc, cach noi
cua viet » ca viet, hoa viet, cua vat
sach hoi » sach doi, sach moi, hoach hoi
hanh dai » hanh tai, hanh dao, vanh dai
hieu van » thien van, lieu va, hieu ve
sang mai » sang ma, sang tai, lang mai
mai hoi » mai khoi, dai hoi, lai hoi
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh

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