Perhaps you should try some spelling variations:
cac thuc » cach thuc, cac thu, can thuc
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
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 » cua te, cuu tre, cua triet
y nang » ly nang, v nang, may nang
ca cua » co 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 ((y nang) OR (ky nang)) ((le hoi) or (ma hoa)). hieu va cac thuc va hanh ca cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y nang) OR (ky nang)) ((le hoi) OR (ma hoa)). hieu va cac thuc va hanh ca cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y nang) OR (ky nang)) ((le hoi) or (ma hoa)). hieu va cac thuc va hanh ca cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) OR (ky nang)) ((le hoi) or (ma hoa)). hieu va cac thuc va hanh ca cua tre*.