Perhaps you should try some spelling variations:
dien cuc » dien tu, dieu cua, vien cac
cau thuc » cau truc, cuu thuc, can thuc
te sach » toc sach
ty nang » ky nang, ty xang, ty hang
va danh » va dinh, va dan, dia danh
va hanh » van hanh, va thanh, ban hanh
hieu ve » hieu va, hieu van
sach ty » sach y, sach tu, sach thu
ve cau » ke cau, va cau, ve cac
cuc te » cua te, cuc thue, cuc tieu
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty nang ((o hoi) OR (o hoc)). hieu ve cau thuc ((va hanh) OR (va danh)) dien cuc te~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty nang ((o hoi) or (o hoc)). hieu ve cau thuc ((va hanh) OR (va danh)) dien cuc te~".
• Adding a wildcard symbol may retrieve word variants: te sach ty nang ((o hoi) or (o hoc)). hieu ve cau thuc ((va hanh) OR (va danh)) dien cuc te*.