Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
thi viet » thi lien
luc ngan » luc nganh, luc nhan, luat ngan
sach ty » sach y, sach tu, sach thu
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
cac luc » cau luc, coc luc, cac nuoc
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 ty ((lang xa) or (van xay)) hoi. hieu ve cac luc ngan ((mai viet) OR (thi viet)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((lang xa) OR (van xay)) hoi. hieu ve cac luc ngan ((mai viet) OR (thi viet)) cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((lang xa) or (van xay)) hoi. hieu ve cac luc ngan ((mai viet) OR (thi viet)) cau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((lang xa) or (van xay)) hoi. hieu ve cac luc ngan ((mai viet) OR (thi viet)) cau tren*.