Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam tu
hanh tai » thanh tai, hang tai, han tai
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cao hoi » cau hoi, co hoi, cao hoc
xa hanh » xa thanh, xa khanh, va hanh
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet

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 cao hoi. hieu van ((nam thuc) or (nam thu)) xa hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang cao hoi. hieu van ((nam thuc) OR (nam thu)) xa hanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang cao hoi. hieu van ((nam thuc) or (nam thu)) xa hanh tai cua tre*.