Perhaps you should try some spelling variations:
vanh tai » van tai, hanh tai, anh tai
van vanh » van anh, van hanh, van manh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
tai cuu » tai cuc, tai buu, tai cua
cac dac » cac dan, cac dai, cac bac
cac duc » cac du, cao duc, cac nuoc
cuu tre » cua tre, cau tren, cau treo
hieu ve » hieu va, hieu van
co hai » co dai, co hoi, so hai
o hai » so hai, o lai, _ hai

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 nang ((o hai) or (co hai)). hieu ve ((cac duc) OR (cac dac)) van vanh tai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hai) OR (co hai)). hieu ve ((cac duc) OR (cac dac)) van vanh tai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hai) or (co hai)). hieu ve ((cac duc) OR (cac dac)) van vanh tai cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hai) or (co hai)). hieu ve ((cac duc) OR (cac dac)) van vanh tai cuu tre*.