Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
tinh tai » trinh tai, tinh thai, tinh hai
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
tang ma » mang may, tang van
lang xa » lang ha, dang xay, lang van
qua cac » cua cac
cac duc » cac du, cao duc, cac dac
duc may » duc mau, duc man, duc manh
cua tre » cua te, cuu tre, dua tren

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 ((tang ma) or (lang xa)) hoi. hieu qua cac duc may tinh tai ((cua tre) OR (cua triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((tang ma) OR (lang xa)) hoi. hieu qua cac duc may tinh tai ((cua tre) OR (cua triet))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((tang ma) or (lang xa)) hoi. hieu qua cac duc may tinh tai ((cua tre) OR (cua triet))*".