Perhaps you should try some spelling variations:
vay doanh » van doanh, ly doanh, voi doanh
va doanh » van doanh, va danh, hoa doanh
su sach » so sach, vu sach
cua cua » cua chua, ca cua, qua cua
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
tang ma » mang may, tang van
mang xa » lang xa, mang may, dang xay
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: su sach ky ((mang xa) OR (tang ma)) hoi. hieu va cac duc ((va doanh) OR (vay doanh)) cua cua 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 cua 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 cua tre*.