Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
va hanh » va thanh, va danh, ban hanh
le tang » le quang, le trung, le thanh
tang xa » trang xa, tang ma, lang xa
sach le » cach le, sach de, sach lo
vai va » mai va, dai va, hai va
va cao » va cac, va co, va dao
ve cac » va cac, vien cac
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: su sach le tang xa hoi. hieu ((ve cac) or (va cao)) suc ((va hanh) OR (van hanh)) vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach le tang xa hoi. hieu ((ve cac) OR (va cao)) suc ((va hanh) OR (van hanh)) vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach le tang xa hoi. hieu ((ve cac) or (va cao)) suc ((va hanh) OR (van hanh)) vai va thiet".
• Adding a wildcard symbol may retrieve word variants: su sach le tang xa hoi. hieu ((ve cac) or (va cao)) suc ((va hanh) OR (van hanh)) vai va thiet*.