Perhaps you should try some spelling variations:
cac thoi » cac toi, cac hop, cac tro
doan thi » dan thi, doanh tai, hoang thi
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
thoi va » hoi va, thai va, tho va
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
dan vi » doan vi, dan va, gan vi

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 ty lang xa hoi. hieu ve cac thoi va ((((dan vi) OR (don vi))) or (doan thi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty lang xa hoi. hieu ve cac thoi va ((((dan vi) OR (don vi))) OR (doan thi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty lang xa hoi. hieu ve cac thoi va ((((dan vi) OR (don vi))) or (doan thi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty lang xa hoi. hieu ve cac thoi va ((((dan vi) OR (don vi))) or (doan thi)) cua tre*.