Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
sach le » cach le, sach de, sach lo
le tang » le quang, le trung, le thanh
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
va giao » van giao, va giai, va gia
va hanh » va thanh, va danh, ban hanh
vai va » mai va, dai va, hai va
thiet » thieu

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 le tang xa hoi. hieu va giao duc ((va hanh) or (van hanh)) vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach le tang xa hoi. hieu va giao duc ((va hanh) OR (van hanh)) vai va thiet.
• Adding a wildcard symbol may retrieve word variants: so sach le tang xa hoi. hieu va giao duc ((va hanh) or (van hanh)) vai va thiet*.