Perhaps you should try some spelling variations:
doanh vai » doanh tai, doanh va, doanh van
ban doanh » van doanh, san doanh, ban danh
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
cuu ban » cuu van, cua ban, cuu san
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
ve cham » va cham, ve chat, vu cham
van hoi » van hoc, van hoe, van loi
ky lang » ky nang, ky dang, ky tang
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: tu sach ky lang ((van hoi) or (van hoa)). hieu ((ve cham) or (ve cac)) cuu ban doanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang ((van hoi) OR (van hoa)). hieu ((ve cham) OR (ve cac)) cuu ban doanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang ((van hoi) or (van hoa)). hieu ((ve cham) or (ve cac)) cuu ban doanh vai cua tre*.