Perhaps you should try some spelling variations:
dua tren » dung tren
ban hang » ngan hang
te sach » toc sach
duc ban » duc tan, duc van, dua ban
cac duc » cac du, cao duc, cac dac
cuu tre » cua tre, cau tren, cau treo
hieu ve » hieu va, hieu van
ky dang » ky nang, ky danh
ky tang » ky nang, kho tang, ky trong
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: te sach ((ky tang) or (ky dang)) xa hoi. hieu ve cac duc ban hang va ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ((ky tang) OR (ky dang)) xa hoi. hieu ve cac duc ban hang va ((dua tren) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: te sach ((ky tang) or (ky dang)) xa hoi. hieu ve cac duc ban hang va ((dua tren) or (cuu tre))*.