Perhaps you should try some spelling variations:
hieu viec » nhieu viec, sieu viet, hieu hien
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
ang xa » lang xa, mang xa, dang xay
xac va » tac va, ac va, bac va
tuc va » thuc va, truc va, tuc xa
ty ang » ty xang, ty hang, ty anh
vi cua » vai cua, di cua

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 ty ang xa hoi. ((hieu viec) OR (hieu ve)) bach ((xac va) or (tuc va)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ang xa hoi. ((hieu viec) OR (hieu ve)) bach ((xac va) OR (tuc va)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty ang xa hoi. ((hieu viec) OR (hieu ve)) bach ((xac va) or (tuc va)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty ang xa hoi. ((hieu viec) OR (hieu ve)) bach ((xac va) or (tuc va)) hanh vi cua tre*.