Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
tu sach » su sach, te sach, tu cach
doan vi » doan va, don vi, doan thi
cac thu » cach thuc, cac thoi
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
thu va » thuc va, thue va, tu va
dan va » doan va, dan ca, ban va
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) OR (thu sach)) ty lang xa hoi. hieu ve cac thu va ((dan va) or (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ty lang xa hoi. hieu ve cac thu va ((dan va) OR (doan vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ty lang xa hoi. hieu ve cac thu va ((dan va) or (doan vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ty lang xa hoi. hieu ve cac thu va ((dan va) or (doan vi)) cua tre*.