Perhaps you should try some spelling variations:
thanh di » thanh doi, thanh de, thanh dinh
thanh do » thanh de, thanh pho, thanh hoa
tu sach » thu sach, su sach, te sach
cao hoi » cau hoi, cao hoc, tao hoi
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, ly nang, v nang
co hoi » co hoc, co loi
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 y nang ((cao hoi) or (co hoi)). hieu ve cac duc va ((thanh di) OR (thanh do)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((cao hoi) OR (co hoi)). hieu ve cac duc va ((thanh di) OR (thanh do)) cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((cao hoi) or (co hoi)). hieu ve cac duc va ((thanh di) OR (thanh do)) cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((cao hoi) or (co hoi)). hieu ve cac duc va ((thanh di) OR (thanh do)) cuu tre*.