Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
hieu ve » hieu va
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
hanh ca » hanh cac, hanh cat, hanh cua
cua tre » cuu tre, cua triet, dua tren
nang o » nang co, nang ho, nang ro
cua te » cua tu
o hai » co hai, so hai, o lai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc sach ky nang o hai. ((hieu ve) or (hieu van)) nam thuc va hanh ca ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc sach ky nang o hai. ((hieu ve) OR (hieu van)) nam thuc va hanh ca ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc sach ky nang o hai. ((hieu ve) or (hieu van)) nam thuc va hanh ca ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: thuoc sach ky nang o hai. ((hieu ve) or (hieu van)) nam thuc va hanh ca ((cua tre) OR (cua te))*.