Perhaps you should try some spelling variations:
va thieu » va thiet, va hieu, va tieu
hieu va » lieu va, hieu qua
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
ty nang » ky nang, ty hang, ly nang
va chat » van chat, va phat, cao chat
bac va » ban va, bac ha, bao va
luc va » duc va, tuc va, loc va
vi va » vi van, vai va, vu 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) OR (ty xang)) mai hoi. hieu va chat ((bac va) or (luc va)) hanh vi va thieu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ty nang) OR (ty xang)) mai hoi. hieu va chat ((bac va) OR (luc va)) hanh vi va thieu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ty nang) OR (ty xang)) mai hoi. hieu va chat ((bac va) or (luc va)) hanh vi va thieu".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty nang) OR (ty xang)) mai hoi. hieu va chat ((bac va) or (luc va)) hanh vi va thieu*.