Perhaps you should try some spelling variations:
nhieu viec » hieu viec, nhien viet
tinh hoc » sinh hoc, tin hoc, hinh hoc
viec cam » viec lam, viec cua, viec va
su sach » vu sach
va tinh » may tinh
cua tre » cua te, cuu tre, cua triet
xay hoi » tay hoi, cay phoi, gay thoi
ky dang » ky nang, ky danh
so sach » so sanh, bo sach, co sach
xuc va » duc va, tuc va, luc va

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) or (so sach)) ky dang ((xay hoi) OR (xa hoi)). nhieu viec cam xuc va tinh hoc cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) ky dang ((xay hoi) OR (xa hoi)). nhieu viec cam xuc va tinh hoc cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) ky dang ((xay hoi) OR (xa hoi)). nhieu viec cam xuc va tinh hoc cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) ky dang ((xay hoi) OR (xa hoi)). nhieu viec cam xuc va tinh hoc cua tre*.