Perhaps you should try some spelling variations:
khanh tai » thanh tai, hanh tai, nhanh thai
van khanh » van thanh, van hanh, van anh
tu sach » thu sach, su sach, te sach
xuc van » duc van, luc van, vuc van
vien da » vien dai, hien dai
sach ky » sac ky, sach y, sach ty
cuc tre » duc tre, cua tre, cuu tre
ve cac » va cac, vien cac
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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 hoi) or (o hai)). hieu ((ve cac) or (vien da)) xuc van khanh tai cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hai)). hieu ((ve cac) OR (vien da)) xuc van khanh tai cuc tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (o hai)). hieu ((ve cac) or (vien da)) xuc van khanh tai cuc tre*.