Perhaps you should try some spelling variations:
vai cua » dai cua, hai cua, lai cua
sach ky » sac ky, sach ty, sach kem
hieu va » lieu va, hieu qua
cac lop » cac hop, cac loai
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
va dan » ca dan, va dau, va dap
va dao » ca dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach ky) or (sach y)) nang xa hoi. hieu va cac lop ((va dan) OR (va dao)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sach y)) nang xa hoi. hieu va cac lop ((va dan) OR (va dao)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (sach y)) nang xa hoi. hieu va cac lop ((va dan) OR (va dao)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sach y)) nang xa hoi. hieu va cac lop ((va dan) OR (va dao)) vai cua tre*.