Perhaps you should try some spelling variations:
hieu luc » hieu luat, hieu qua
va thanh » gia thanh, ban thanh, va tinh
hieu tuc » hieu thuc, hieu thuoc, lieu thuc
va danh » va dinh, va dan, va hanh
so sach » so sanh, bo sach, co sach
nang xa » nang x, lang xa, nang ma
sach vu » sach va, sach tu, sach uu
vu nang » vuc nang, va nang, vu dang
lai hoa » dai hoa, loai hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach vu nang xa hoi. ((hieu tuc) or (hieu luc)) nang luc ((va danh) or (va thanh)) lai hoa viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach vu nang xa hoi. ((hieu tuc) OR (hieu luc)) nang luc ((va danh) OR (va thanh)) lai hoa viet.
• Adding a wildcard symbol may retrieve word variants: so sach vu nang xa hoi. ((hieu tuc) or (hieu luc)) nang luc ((va danh) or (va thanh)) lai hoa viet*.