Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, le thanh
tu sach » thu sach, su sach, te sach
cao hoc » cho hoc, chat hoc
hieu ve » hieu va, hieu van
va tinh » may tinh
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, ly nang, v nang
ve cac » va cac, vien cac
cac tu » cac thu, cach tu, cac du
di cuu » di cau, di cua, dinh cuu

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 hoc) OR (co hoc)). hieu ve cac tu ((va thanh) or (va tinh)) di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((cao hoc) OR (co hoc)). hieu ve cac tu ((va thanh) OR (va tinh)) di cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((cao hoc) OR (co hoc)). hieu ve cac tu ((va thanh) or (va tinh)) di cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((cao hoc) OR (co hoc)). hieu ve cac tu ((va thanh) or (va tinh)) di cuu tre*.