Perhaps you should try some spelling variations:
cao thuoc » cay thuoc, cua thuoc, nam thuoc
cao quoc » cac quoc, han quoc, cua quoc
ban banh » ban hanh, ban anh, ban danh
hieu van » hieu va, thien van, lieu va
banh vi » hanh vi, ban vi, benh vi
tu sach » thu sach, su sach, te sach
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 quoc) OR (cao thuoc)) 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 quoc) OR (cao thuoc)) 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 quoc) OR (cao thuoc)) 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 quoc) OR (cao thuoc)) ban banh vi cua tre*.