Perhaps you should try some spelling variations:
hieu luat » hieu qua
hieu vuc » hieu luc, hieu tuc, hieu thuc
hanh tai » thanh tai, hang tai, han tai
so sach » so sanh, bo sach, co sach
nang ma » tang ma, sang ma, nang cao
va hanh » van hanh, va thanh, va danh
ca viet » va viet, co viet, hoa viet
y nang » ky nang, ly nang, v nang
ma hoi » mai hoi, xa hoi, ma hoa
luc va » duc va, tuc va, loc va
tai ca » tai cac, tai cao, tai cua

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 y nang ma hoi. ((hieu vuc) or (hieu luat)) nang luc va hanh tai ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y nang ma hoi. ((hieu vuc) OR (hieu luat)) nang luc va hanh tai ca viet.
• Adding a wildcard symbol may retrieve word variants: so sach y nang ma hoi. ((hieu vuc) or (hieu luat)) nang luc va hanh tai ca viet*.