Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
so sach » so sanh, bo sach, co sach
sach ty » sach y, sach tu, sach thu
mai hoi » mai khoi, dai hoi, lai hoi
hieu ve » hieu va, hieu van
luc van » luoc van, luu van, luc va
duc van » duc va, duc tan, duc manh
ma hoi » xa hoi, ma hoa, me hoi
ve cau » ke cau, va cau, ve cac
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty xang ((ma hoi) or (mai hoi)). hieu ve cau ((luc van) OR (duc van)) hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty xang ((ma hoi) OR (mai hoi)). hieu ve cau ((luc van) OR (duc van)) hanh vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty xang ((ma hoi) or (mai hoi)). hieu ve cau ((luc van) OR (duc van)) hanh vi cua viet".
• Adding a wildcard symbol may retrieve word variants: so sach ty xang ((ma hoi) or (mai hoi)). hieu ve cau ((luc van) OR (duc van)) hanh vi cua viet*.