Perhaps you should try some spelling variations:
ban banh » ban hanh, ban anh, ban danh
quoc ban » quoc bao, quoc lan, quoc quan
tu sach » thu sach, su sach, te sach
van hao » van dao, van ha, van bao
banh vi » hanh vi, ban vi, benh vi
van cao » van dao, van bao, van cau
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di 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 ((ky lang) or (ky dang)) xa hoi. hieu ((van cao) OR (van hao)) quoc ban banh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky dang)) xa hoi. hieu ((van cao) OR (van hao)) quoc ban banh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) or (ky dang)) xa hoi. hieu ((van cao) OR (van hao)) quoc ban banh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) or (ky dang)) xa hoi. hieu ((van cao) OR (van hao)) quoc ban banh vi cua tre*.