Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
kho tang » cao tang
lai hoi » dai hoi, lai hoa, lai roi
ky sang » ky nang, ky dang, ky tang
cac loc » cac lop, cac toc, cac hoc
hieu ve » hieu va, hieu van
ve cac » vien cac
loc va » hoc va, luc va
va dau » va dao
va cau » van cau, va cao, va cai

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((ky sang) or (kho tang)) lai hoi. hieu ve cac loc va dau ((va cau) OR (va cac)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky sang) OR (kho tang)) lai hoi. hieu ve cac loc va dau ((va cau) OR (va cac)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ky sang) or (kho tang)) lai hoi. hieu ve cac loc va dau ((va cau) OR (va cac)) tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ky sang) or (kho tang)) lai hoi. hieu ve cac loc va dau ((va cau) OR (va cac)) tren*.