Perhaps you should try some spelling variations:
van thiet » va thiet, dan thiet, can thiet
ban hanh » ban hang
sach doi » sach moi, sach dao, sach bai
sach hoi » sach moi, cach thoi, hoach hoi
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
cau luc » cau truc, cau phuc
va danh » va dinh, va dan, va hanh
ma hoi » mai hoi, xa hoi, ma hoa
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) OR (sach hoi)) nang 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) OR (sach hoi)) nang 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) OR (sach hoi)) nang ma hoi. hieu va cau luc ((va danh) or (ban hanh)) vi van thiet*.