Perhaps you should try some spelling variations:
thanh do » thanh pho, thanh hoa, thanh loi
thanh de » hanh de, thanh ve, thanh le
te sach » toc sach
sach ky » sac ky, sach y, sach ty
cac dac » cac dan, cac dai, cac bac
dau hoi » dai hoi, dan hoi, dau noi
hieu ve » hieu va, hieu van
cuu tre » cua tre, cau tren, cau treo
ve cac » va cac, vien cac
dac va » duc va, day va, dat va

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky nang ((dau hoi) OR (cau hoi)). hieu ve cac dac va ((thanh de) or (thanh do)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky nang ((dau hoi) OR (cau hoi)). hieu ve cac dac va ((thanh de) OR (thanh do)) cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky nang ((dau hoi) OR (cau hoi)). hieu ve cac dac va ((thanh de) or (thanh do)) cuu tre".
• Adding a wildcard symbol may retrieve word variants: te sach ky nang ((dau hoi) OR (cau hoi)). hieu ve cac dac va ((thanh de) or (thanh do)) cuu tre*.