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
nang xa » nang x, lang xa, nang ma
hieu ve » hieu van
hieu va » lieu va, hieu qua
cua cua » cua chua, ca cua, qua cua
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 nang xa hoi. ((hieu ve) OR (hieu va)) 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 nang xa hoi. ((hieu ve) OR (hieu va)) cac ((duc va) OR (tuc va)) doanh cua cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. ((hieu ve) OR (hieu va)) cac ((duc va) or (tuc va)) doanh cua cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. ((hieu ve) OR (hieu va)) cac ((duc va) or (tuc va)) doanh cua cua tre*.