Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
hieu van » hieu va, thien van, lieu va
danh sai » dung sai, danh bat, danh dau
va danh » va dinh, va dan, va hanh
cac duc » cac du, cao duc, cac dac
tu sach » thu sach, su sach, te sach
hieu ve » hieu va
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
sai va » mai va, dai va, hai va

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 ((ky lang) or (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac duc va danh sai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac duc va danh sai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) or (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac duc va danh sai va triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) or (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac duc va danh sai va triet*.