Perhaps you should try some spelling variations:
doanh cua » doanh luan
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cua cua » cua chua, ca cua, qua cua
lang xa » lang ha, dang xay, lang van
hieu ve » hieu va, hieu van
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, truc va, tuc xa

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 ky lang xa hoi. ((hieu ve) or (hieu qua)) cac ((duc va) or (tuc va)) doanh cua cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang xa hoi. ((hieu ve) OR (hieu qua)) cac ((duc va) OR (tuc va)) doanh cua cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang xa hoi. ((hieu ve) or (hieu qua)) cac ((duc va) or (tuc va)) doanh cua cua tre*.