Perhaps you should try some spelling variations:
vay doanh » van doanh, ly doanh, voi doanh
chua tre » chua tri, cua tre, chua trieu
cua chua » sua chua, cua chu, cua nhua
va doanh » van doanh, va danh, hoa doanh
cac duc » cac du, cao duc, cac dac
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
tang ma » mang may, tang van
mang xa » lang xa, mang may, dang xay
hieu va » lieu va, hieu qua

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 ((mang xa) or (tang ma)) hoi. hieu va cac duc ((va doanh) OR (vay doanh)) cua chua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((mang xa) OR (tang ma)) hoi. hieu va cac duc ((va doanh) OR (vay doanh)) cua chua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((mang xa) or (tang ma)) hoi. hieu va cac duc ((va doanh) OR (vay doanh)) cua chua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((mang xa) or (tang ma)) hoi. hieu va cac duc ((va doanh) OR (vay doanh)) cua chua tre*.