Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
chat duc » chat xuc, chat doc, chet duoc
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
hieu va » lieu va, hieu qua
duc van » duc va, duc tan, duc manh
y nang » ky nang, ly nang, v nang
x hoi » xa hoi, o hoi, x ho
va va » va vua, va vai, va vat

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 x hoi. ((hieu van) or (hieu va)) chat duc van hanh ((va va) OR (va van)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y nang x hoi. ((hieu van) OR (hieu va)) chat duc van hanh ((va va) OR (va van)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y nang x hoi. ((hieu van) or (hieu va)) chat duc van hanh ((va va) OR (va van)) triet".
• Adding a wildcard symbol may retrieve word variants: so sach y nang x hoi. ((hieu van) or (hieu va)) chat duc van hanh ((va va) OR (va van)) triet*.