Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach y, sach ty
va hang » van hang, va nang, va lang
su sach » so sach, vu sach
nam luc » nang luc, nhan luc, nam duoc
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
di cu » di cau, di cua, da cu
di du » li du

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

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