Perhaps you should try some spelling variations:
van doanh » toan doanh, van thanh, van anh
hieu van » hieu va, thien van, lieu va
van cam » van nam, van lam, van cau
sach ty » sach y, sach tu, sach thu
tu sach » thu sach, su sach, te sach
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
cua tre » cua te, cuu tre, cua triet
cam so » nam so, ham so, cam lo
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ty ((nang xa) or (lang xa)) hoi. hieu van cam so ((van doanh) OR (van dong)) va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang xa) OR (lang xa)) hoi. hieu van cam so ((van doanh) OR (van dong)) va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((nang xa) or (lang xa)) hoi. hieu van cam so ((van doanh) OR (van dong)) va cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) or (lang xa)) hoi. hieu van cam so ((van doanh) OR (van dong)) va cua tre*.