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