Perhaps you should try some spelling variations:
can thiet » dan thiet, cac thiet, cad thiet
ban hanh » ban hang
sach dao » lanh dao
va danh » va dinh, va dan, va hanh
cau luc » cau truc, cau phuc
vu sach » vu bach, su sach, vu khach
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
hieu va » lieu va, hieu qua
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.

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach dao ((nang xa) or (nang ma)) hoi. hieu va cau luc ((va danh) or (ban hanh)) vi can thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach dao ((nang xa) OR (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 dao ((nang xa) or (nang ma)) hoi. hieu va cau luc ((va danh) or (ban hanh)) vi can thiet*.