Perhaps you should try some spelling variations:
trinh viet » ninh viet, trinh vat
va trinh » van trinh, va tinh, lap trinh
vu khach » vu khanh, vu khac, vay khach
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
cua tre » cua te, cua triet, dua tren
van bac » van ban, van bao, van hac
bac loc » bac hoc
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
cuu tre » cau tren, cau treo
loc va » hoc va, luc 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 khach)) ky tang xa hoi. hieu van bac loc va trinh viet ((cua tre) OR (cuu tre))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (vu khach)) ky tang xa hoi. hieu van bac loc va trinh viet ((cua tre) OR (cuu tre))~".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu khach)) ky tang xa hoi. hieu van bac loc va trinh viet ((cua tre) OR (cuu tre))*.