Perhaps you should try some spelling variations:
hieu ve » hieu va, hieu van
dinh du » dinh duc, dinh cu, dinh tu
dinh di » dinh vi, danh di, dinh da
ve pham » vi pham, v pham, ve phan
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
dai hoi » dai hoc, dai hai, dai moi
dau hoi » cau hoi, dan hoi, dau noi
ty nang » ky nang, ty xang, ty hang
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: tu sach ty nang ((dau hoi) or (dai hoi)). hieu ve pham duc va ((dinh di) OR (dinh du)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((dau hoi) OR (dai hoi)). hieu ve pham duc va ((dinh di) OR (dinh du)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((dau hoi) or (dai hoi)). hieu ve pham duc va ((dinh di) OR (dinh du)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((dau hoi) or (dai hoi)). hieu ve pham duc va ((dinh di) OR (dinh du)) cua tre*.