Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
y nang » ky nang, ly nang, v nang
bao va » bao ve, tao va, ban va
vi cua » vai cua, di cua
cua te » cua tu
bo va » do va, so va, co va

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 y nang mai hoi. ((hieu ve) or (hieu qua)) bao ((bo va) or (bao va)) hanh vi cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang mai hoi. ((hieu ve) OR (hieu qua)) bao ((bo va) OR (bao va)) hanh vi cua te.
• Adding a wildcard symbol may retrieve word variants: su sach y nang mai hoi. ((hieu ve) or (hieu qua)) bao ((bo va) or (bao va)) hanh vi cua te*.