Perhaps you should try some spelling variations:
khanh tai » thanh tai, hanh tai, nhanh thai
van khanh » van thanh, van hanh, van anh
vien cac » vien bach, vien dai, vien da
tu sach » thu sach, su sach, te sach
duc van » duc va, duc tan, duc manh
cuc tre » duc tre, cua tre, cuu tre
sach ky » sac ky, sach y, sach ty
co dai » co dan, do dai
ve cac » va cac
o hai » co hai, so hai, o lai

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