Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, hieu ve
van hanh » van thanh, ban hanh, van anh
va triet » va thiet, va trien, ve triet
tu sach » thu sach, su sach, te sach
tang ma » mang may, tang van
lam luc » lao luc, lam duoc
luc van » luoc van, luu van, duc van
hanh de » hanh ve, hanh kem
de va » de van, te va, ke 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 y ((nang cao) or (tang ma)) hoi. ((hieu van) OR (lieu va)) lam luc van hanh de va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang cao) OR (tang ma)) hoi. ((hieu van) OR (lieu va)) lam luc van hanh de va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang cao) or (tang ma)) hoi. ((hieu van) OR (lieu va)) lam luc van hanh de va triet".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang cao) or (tang ma)) hoi. ((hieu van) OR (lieu va)) lam luc van hanh de va triet*.