Perhaps you should try some spelling variations:
hang doi » hang di, hang loi, huong doi
hieu van » thien van, lieu va, hieu ve
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
va hang » van hang, va nang, va lang
nam luc » nang luc, nhan luc, nam duoc
hieu va » lieu va, hieu qua
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
co tren » cu tren, do tren, ca tren
doi co » doi bo, moi co, hoi co

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 tang xa hoi. ((hieu van) OR (hieu va)) ((nam luc) or (nam thuc)) va hang doi co tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky tang xa hoi. ((hieu van) OR (hieu va)) ((nam luc) OR (nam thuc)) va hang doi co tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky tang xa hoi. ((hieu van) OR (hieu va)) ((nam luc) or (nam thuc)) va hang doi co tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky tang xa hoi. ((hieu van) OR (hieu va)) ((nam luc) or (nam thuc)) va hang doi co tren*.