Perhaps you should try some spelling variations:
duoc tren » nuoc tren, thuoc tren, dung tren
thien van » thi van
nam thuc » nam thuoc, am thuc, nam thu
doi duoc » doi cuoc, do duoc, dong duoc
hang doi » hang di, hang loi, huong doi
va hang » van hang, va nang, va lang
tu sach » thu sach, su sach, te sach
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
nam duc » nam duoc, pham duc, nam buoc

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 ((ky lang) or (ky dang)) xa hoi. thien van ((nam duc) OR (nam thuc)) va hang doi duoc tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky dang)) xa hoi. thien van ((nam duc) OR (nam thuc)) va hang doi duoc tren*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) or (ky dang)) xa hoi. thien van ((nam duc) OR (nam thuc)) va hang doi duoc tren*".