Perhaps you should try some spelling variations:
van doanh » toan doanh, van dong, van thanh
doc sach » hoc sach, toc sach, nuoc sach
va doanh » vay doanh, va danh, hoa doanh
sach ky » sac ky, sach y, sach ty
nang ho » nang hoc, tang ho, nang cao
nang co » nang cao, nang doc, nang noi
hieu va » lieu va, hieu qua
cua te » cua tu
va am » va lam, va cam

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ky ((nang ho) or (nang co)) hoi. hieu va am thuc ((va doanh) OR (van doanh)) tri cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky ((nang ho) OR (nang co)) hoi. hieu va am thuc ((va doanh) OR (van doanh)) tri cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ky ((nang ho) or (nang co)) hoi. hieu va am thuc ((va doanh) OR (van doanh)) tri cua te".
• Adding a wildcard symbol may retrieve word variants: doc sach ky ((nang ho) or (nang co)) hoi. hieu va am thuc ((va doanh) OR (van doanh)) tri cua te*.