Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
nang cau » nang cao, hang cau, nang dau
cam tuc » cam xuc, cam tu, nam thuc
vai cua » dai cua, hai cua, lai cua
va hanh » va thanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach ty, sach kem
hieu va » lieu va, hieu qua
va cam » va cham, va cac, va cao

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

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