Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
xa thanh » va thanh, ha thanh, ta thanh
thanh vi » hanh vi, thanh va, thanh ve
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nam tuc » nam thuc, nam truc, nam tu
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
o hoc » co hoc, mo hoc, so hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang ((o hoc) or (xa hoi)). hieu van nam tuc xa thanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((o hoc) OR (xa hoi)). hieu van nam tuc xa thanh vi ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((o hoc) or (xa hoi)). hieu van nam tuc xa thanh vi ((cua tre) or (cuu tre))*.