Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
cac dac » cac dai, cac bac, cac tac
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
ty sang » ty xang, ty hang, duy sang

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 sang ((ma hoa) or (xa hoi)). hieu ve ((cac dac) OR (cac dan)) van hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty sang ((ma hoa) OR (xa hoi)). hieu ve ((cac dac) OR (cac dan)) van hanh tai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty sang ((ma hoa) or (xa hoi)). hieu ve ((cac dac) OR (cac dan)) van hanh tai cua tre*".