Perhaps you should try some spelling variations:
giai duc » giao duc, gia duc, giap duc
hanh vai » hanh vi, hanh va, hanh tai
su sach » so sach, vu sach
sach le » cach le, sach de, sach lo
xang xa » lang xa, ang xa, dang xay
mang xa » lang xa, mang may, dang xay
hieu va » lieu va
va hanh » van hanh, va thanh, va danh
vai va » mai va, dai va, hai va
thiet » thieu

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 le ((xang xa) or (mang xa)) hoi. ((hieu va) OR (hieu qua)) giai duc va hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach le ((xang xa) OR (mang xa)) hoi. ((hieu va) OR (hieu qua)) giai duc va hanh vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach le ((xang xa) or (mang xa)) hoi. ((hieu va) OR (hieu qua)) giai duc va hanh vai va thiet".
• Adding a wildcard symbol may retrieve word variants: su sach le ((xang xa) or (mang xa)) hoi. ((hieu va) OR (hieu qua)) giai duc va hanh vai va thiet*.