Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
ban hanh » ban hang
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
x hoi » xa hoi, o hoi, x ho

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. hieu van nam thuc ((vat thanh) OR (ban hanh)) vi ((cuu tre) OR (cua tre))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. hieu van nam thuc ((vat thanh) or (ban hanh)) vi ((cuu tre) OR (cua tre))~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. hieu van nam thuc ((vat thanh) or (ban hanh)) vi ((cuu tre) OR (cua tre))*.