Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
va doanh » van doanh, vay doanh, va danh
doanh ca » doanh cua, doanh cao, doanh va
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
ca cua » co cua
cua te » cua tu

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky ((nang x) OR (nang cao)) hoi. hieu va cac duc va doanh ca cua te~.
• Adding a wildcard symbol may retrieve word variants: thu sach ky ((nang x) or (nang cao)) hoi. hieu va cac duc va doanh ca cua te*.