Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hanh tai » thanh tai, hang tai, han tai
sua viet » su viet, cua viet, lua viet
tu sach » thu sach, su sach, te sach
so sach » so sanh, bo sach, co sach
ky tang » ky nang, ky dang, kho tang
tang ma » mang may, tang van
qua cac » cua cac
cac tuc » cac toc, cac tu, cac tac
tuc van » thuc van, truc van, tuc va
tai sua » dai sua, tai su, tai cua
ma hoi » mai hoi, xa hoi, ma hoa

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) or (so sach)) ky tang ma hoi. hieu qua cac tuc van hanh tai sua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (so sach)) ky tang ma hoi. hieu qua cac tuc van hanh tai sua viet.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (so sach)) ky tang ma hoi. hieu qua cac tuc van hanh tai sua viet*.