Perhaps you should try some spelling variations:
va doanh » van doanh, vay doanh, va danh
dang cau » hang cau, bang cau, dang mau
sach ky » sac ky, sach y, sach kem
tai cua » thai cua, tai cuc, tri cua
va cham » va chat, va tham
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
luc va » duc va, tuc va, loc va
va cam » va cac, 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: tu ((sach ky) OR (sach ty)) dang cau hoi. hieu ((va cam) or (va cham)) luc va doanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach ty)) dang cau hoi. hieu ((va cam) OR (va cham)) luc va doanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sach ty)) dang cau hoi. hieu ((va cam) or (va cham)) luc va doanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sach ty)) dang cau hoi. hieu ((va cam) or (va cham)) luc va doanh tai cua tre*.