Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
tai cua » thai cua, tai cuc, tri cua
dua ban » dia ban, cua ban, qua ban
nam dua » nam da, nam cua, nam mua
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach kem
mai hoi » mai khoi, dai hoi, lai hoi
sach ty » sach y, sach tu, sach thu

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) or (sach ty)) nang ((mai hoi) or (ma hoa)). hieu van nam dua ban thanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach ty)) nang ((mai hoi) OR (ma hoa)). hieu van nam dua ban thanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sach ty)) nang ((mai hoi) or (ma hoa)). hieu van nam dua ban thanh tai cua tre*.