Perhaps you should try some spelling variations:
va doanh » van doanh, vay doanh, va danh
tu sach » thu sach, su sach, te sach
lang xa » lang ha, dang xay, lang van
qua cam » qua cham, qua cac, qua ca
cam duc » cam xuc, cao duc, pham duc
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet

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 y ((mang may) or (lang xa)) hoi. hieu qua cam duc va doanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((mang may) OR (lang xa)) hoi. hieu qua cam duc va doanh tai cua tre*.