Perhaps you should try some spelling variations:
doanh van » doan van, doanh va, doanh ban
danh vai » danh sai, danh va, dang van
tu sach » thu sach, su sach, te sach
cac cua » cach cua, cac qua, ca cua
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
tang ma » mang may, tang van
tang xa » trang xa, lang xa, tang ha
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac

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