Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thanh van » thanh san, thanh toan, thanh phan
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
ky tang » ky dang, kho tang, ky trong
lam duc » lam duoc, nam duoc, lam dung
van cua » vang cua, ban cua, dan 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: su sach ((ky tang) OR (ky nang)) xa hoi. hieu van ((lam duc) or (pham duc)) ban thanh van cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ky tang) OR (ky nang)) xa hoi. hieu van ((lam duc) OR (pham duc)) ban thanh van cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ky tang) OR (ky nang)) xa hoi. hieu van ((lam duc) or (pham duc)) ban thanh van cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ky tang) OR (ky nang)) xa hoi. hieu van ((lam duc) or (pham duc)) ban thanh van cua tre*.