Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
sach thu » sach thue, sach thieu, sach tham
hieu van » hieu va, thien van, lieu va
dao thuc » dan thuc, dao tuc, do thuc
vat hanh » vat thanh, van hanh, va hanh
hanh dai » hanh tai, hanh dao, vanh dai
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, dang xay, lang van
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 ky) or (sach thu)) lang xa hoi. hieu van dao thuc vat hanh dai ((cua tre) OR (cua triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach thu)) lang xa hoi. hieu van dao thuc vat hanh dai ((cua tre) OR (cua triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sach thu)) lang xa hoi. hieu van dao thuc vat hanh dai ((cua tre) OR (cua triet))".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sach thu)) lang xa hoi. hieu van dao thuc vat hanh dai ((cua tre) OR (cua triet))*.