Perhaps you should try some spelling variations:
trinh viet » ninh viet, trinh vat
viet cua » viec cua, viet ca, viet qua
hieu van » hieu va, thien van, lieu va
su sach » so sach
van bac » van ban, van bao, van hac
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
vu sach » vu bach, vu khach
cua tre » cua te, cuu tre, cua triet
loc va » hoc va
luc va » duc va, tuc va

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: ((su sach) OR (vu sach)) ky tang xa hoi. hieu van bac ((loc va) OR (luc va)) trinh viet cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (vu sach)) ky tang xa hoi. hieu van bac ((loc va) OR (luc va)) trinh viet cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu sach)) ky tang xa hoi. hieu van bac ((loc va) OR (luc va)) trinh viet cua tre*.