Perhaps you should try some spelling variations:
van khanh » van thanh, van hanh, van anh
van nhanh » van thanh, van hanh, van nhan
sach doi » sach hoi, sach moi, sach dao
tu sach » thu sach, su sach, te sach
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
cam duc » cam xuc, cao duc, pham duc
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
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: tu sach doi ((nang xa) or (lang xa)) hoi. hieu va cam duc ((van nhanh) OR (van khanh)) hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi ((nang xa) OR (lang xa)) hoi. hieu va cam duc ((van nhanh) OR (van khanh)) hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach doi ((nang xa) or (lang xa)) hoi. hieu va cam duc ((van nhanh) OR (van khanh)) hai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach doi ((nang xa) or (lang xa)) hoi. hieu va cam duc ((van nhanh) OR (van khanh)) hai cua tre*.