Perhaps you should try some spelling variations:
va thieu » va thiet, va hieu, va tieu
hanh vai » hanh vi, hanh va, hanh tai
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
tu sach » thu sach, su sach, te sach
lai hoi » dai hoi, lai hoa, lai roi
mai hoi » mai khoi, dai hoi, mai doi
ty nang » ky nang, ty xang, ty hang
ve chat » va chat, van chat
xuc va » duc va, tuc va, xac va
luc va » duc va, tuc va, loc va
vai va » mai va, dai va, hai va

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 ((mai hoi) OR (lai hoi)). hieu ve chat ((xuc va) or (luc va)) hanh vai va thieu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((mai hoi) OR (lai hoi)). hieu ve chat ((xuc va) OR (luc va)) hanh vai va thieu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((mai hoi) OR (lai hoi)). hieu ve chat ((xuc va) or (luc va)) hanh vai va thieu".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((mai hoi) OR (lai hoi)). hieu ve chat ((xuc va) or (luc va)) hanh vai va thieu*.