Perhaps you should try some spelling variations:
van doanh » toan doanh, van dong, van thanh
toc sach » hoc sach, doc sach, thuoc sach
va doanh » vay doanh, va danh, hoa doanh
hieu van » hieu va, thien van, lieu va
dan cua » dan ca, ban cua, dai cua
van cac » van hac, van cau, van bac
cac toc » cac toi, cac nuoc, cac thoi
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
cua tre » cua te, cuu tre, cua triet

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

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