Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
doanh van » doan van, doanh va, doanh ban
va doanh » van doanh, vay doanh, va danh
hau tren » dau tren, cau tren, thai tren
kho tang » cao tang
lai hoi » dai hoi, lai hoa, lai roi
ky sang » ky nang, ky dang, ky tang
van hau » van ha, van hai, van dau
ve cam » ve cham, va cam, ve cai
ve cac » va cac, vien cac

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

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