Perhaps you should try some spelling variations:
vay doanh » van doanh, ly doanh, voi doanh
va doanh » van doanh, va danh, hoa doanh
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
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 ty ((mang may) or (lang xa)) hoi. hieu qua cam duc ((va doanh) OR (vay doanh)) tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((mang may) OR (lang xa)) hoi. hieu qua cam duc ((va doanh) OR (vay doanh)) tai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((mang may) or (lang xa)) hoi. hieu qua cam duc ((va doanh) OR (vay doanh)) tai cua tre*".