Perhaps you should try some spelling variations:
ban hanh » ban hang
van hanh » van thanh, van anh, van ban
te sach » toc sach
doi cua » dai cua, hoi cua
cac duc » cac du, cao duc, cac dac
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
cua tu » cua tuc, cua su, cua cu

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((nang ma) OR (tang ma)) hoi. hieu va cac duc ((van hanh) OR (ban hanh)) doi cua tu~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((nang ma) OR (tang ma)) hoi. hieu va cac duc ((van hanh) or (ban hanh)) doi cua tu~".
• Adding a wildcard symbol may retrieve word variants: te sach ty ((nang ma) OR (tang ma)) hoi. hieu va cac duc ((van hanh) or (ban hanh)) doi cua tu*.