Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
va nang » van nang, da nang, cam nang
va hang » van hang, va lang, va hanh
du tren » dua tren, dau tren, duc tren
sach ky » sac ky, sach y, sach ty
lang ha » long ha
ky lang » ky nang, ky dang, ky tang
ha hoi » hoa hoi, ha noi, xa hoi
di du » li du

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: tu sach ky lang ha hoi. hieu van ((nang luc) OR (nam thuc)) ((va hang) OR (va nang)) di du tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky lang ha hoi. hieu van ((nang luc) or (nam thuc)) ((va hang) OR (va nang)) di du tren~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang ha hoi. hieu van ((nang luc) or (nam thuc)) ((va hang) OR (va nang)) di du tren*.