Perhaps you should try some spelling variations:
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
bac va » ban va, bac ha, tac va
y nang » ky nang, ly nang, v nang
bao va » bao ve, tao va, ban va
bi van » bui van, vi van, binh van
x hoi » xa hoi, o hoi, x ho
bi va » bo 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 x hoi. hieu ve cac ((bac va) or (bao va)) tinh ((bi va) or (bi van)) thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang x hoi. hieu ve cac ((bac va) OR (bao va)) tinh ((bi va) OR (bi van)) thiet.
• Adding a wildcard symbol may retrieve word variants: su sach y nang x hoi. hieu ve cac ((bac va) or (bao va)) tinh ((bi va) or (bi van)) thiet*.