Perhaps you should try some spelling variations:
can thiet » dan thiet, cac thiet, cad thiet
sach doi » sach hoi, sach moi, sach dao
doi nang » dai nang, hoi nang, voi nang
ban hanh » ban hang
vu sach » vu bach, su sach, vu khach
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
vi can » voi can, vi van, i can

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 hoi. hieu va cau luc ((va danh) OR (ban hanh)) vi can thiet~.
• Adding a wildcard symbol may retrieve word variants: vu sach doi nang ma hoi. hieu va cau luc ((va danh) or (ban hanh)) vi can thiet*.