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