Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thuc van » thuc vat, thuc dan, thuc va
van hanh » van thanh, ban hanh, van anh
hanh dai » hanh tai, hanh dao, vanh dai
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
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: su ((sach y) or (sac ky)) nang ma hoi. ((hieu ve) OR (hieu van)) am thuc van hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach y) OR (sac ky)) nang ma hoi. ((hieu ve) OR (hieu van)) am thuc van hanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach y) or (sac ky)) nang ma hoi. ((hieu ve) OR (hieu van)) am thuc van hanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach y) or (sac ky)) nang ma hoi. ((hieu ve) OR (hieu van)) am thuc van hanh dai cua tre*.