Perhaps you should try some spelling variations:
sach ky » sac ky, sach ty, sach kem
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, ban hanh
va danh » va dinh, va dan, dia danh
cac lop » cac hop, cac loai
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
x hoi » xa hoi, o hoi, x ho

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