Perhaps you should try some spelling variations:
van thiet » va thiet, dan thiet, can thiet
sach doi » sach hoi, sach moi, sach dao
ban hanh » ban hang
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
hieu va » lieu va, hieu qua
cau luc » cau truc, cau phuc
va danh » va dinh, va dan, va hanh
vu sach » vu bach, su sach, vu khach
va cau » van cau, va cac, va dau

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: vu sach doi ((nang ma) OR (tang ma)) hoi. hieu va cau luc ((va danh) OR (ban hanh)) vi van thiet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach doi ((nang ma) OR (tang ma)) hoi. hieu va cau luc ((va danh) or (ban hanh)) vi van thiet~".
• Adding a wildcard symbol may retrieve word variants: vu sach doi ((nang ma) OR (tang ma)) hoi. hieu va cau luc ((va danh) or (ban hanh)) vi van thiet*.