Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
hieu van » hieu va, thien van, lieu va
thuc dan » thuc hanh, hoc dan, thuc vat
hieu ve » hieu va
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc day
hanh ca » hanh cac, hanh cat, hanh cua
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
ca cua » co cua
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) OR (thuc dan)) hanh ca cua tre~.
• 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) OR (thuc dan)) hanh ca cua tre.
• 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) OR (thuc dan)) hanh ca cua tre".
• Adding a wildcard symbol may retrieve word variants: thuoc sach ky nang o hai. ((hieu ve) or (hieu van)) nam ((thuc va) OR (thuc dan)) hanh ca cua tre*.